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The catalytic cracking process is one of the important processes in the secondary processing of petroleum. The only proper way to monitor a catalytic cracking unit is to regularly examine its material balance, heat balance, and pressure balance. By regularly collecting and analyzing the material balance and heat balance of the plant’s operation, it is possible to gain a better understanding of the plant’s operational history and current status, predict its future, and lay the foundation for optimizing plant operations. Any changes in feed quality, operating conditions, catalyst, and equipment condition will affect the material balance and heat balance of the plant. To gain a thorough understanding of the material and heat balances in the operation of a device, it is first necessary to carry out the calculations for these balances correctly. To this end, this paper first introduces the calculation methods for the material balance and heat balance of catalytic cracking. Section 1: Measurement 1. Oil product measurement Generally, there are two methods for measuring oil products: tank gauging/volume measurement of transported oil, and measurement using online differential pressure flow meters. 1.1 Tank gauging/transfer volume method: The tank gauging/transfer volume method is one of the most widely used and relatively accurate methods in refineries. When measuring the oil volume by using tank gauging/transfer volume, calculations should be carried out in accordance with the **standard GB/T 1885—1998 for petroleum measurement tables. Oil meters are established categorized by crude oil, products, and lubricants. It is now adopted in most parts of the world and is more universal in oil trade. Both the feedstocks and products used in catalytic cracking should utilize the petroleum metering table – product section. Glass hydrometers are used for oil metering. GB/T 1885—1998 “Oil Measuring Tables” – A brief description of the product-related sections and their usage is as follows: 1.1.1 Composition of oil measuring tables: Standard density tables: Table 59A, Table 59B, Table 59D; Volume correction coefficient tables: Table 60A, Table 60B, Table 60D; Other oil measuring tables: Table E1, Table E2, Table E3, Table E4. Table 59B – Standard density table for products, and Table 60B – Volume correction coefficient table for products, are part of GB/T 1885—1998 “Oil Measuring Tables”. Table 59B is used for petroleum products other than lubricating oils, and the standard density (density at 20°C) is obtained by looking up the apparent density (densitometer reading) at the known test temperature. Table 60B is used for petroleum products other than lubricating oils; it provides the volume correction factor (VCF20), which is used to adjust the volume at the measurement temperature to the standard volume (volume at 20°C), by referring to the standard density and the measurement temperature. 1.1.2 Product measurement: The quantity of products is calculated based on their mass in the air. When the apparent density of a product is measured using a petroleum densitometer at a non-standard temperature, its standard density (ρ20) should be looked up in Table 59B. When calculating the quantity of a product, its volume at the measurement temperature must usually be converted to a standard volume. The standard volume of the product (V20) is obtained by multiplying the volume at the measurement temperature (Vt) by the volume correction factor (VCF20) that adjusts the volume from the measurement temperature to the standard volume, as shown in Equation (1). The volume correction factor is obtained from Table 60B using the standard density and the measurement temperature. V20=Vt × VCF20…………………(1) To calculate the mass of the product in air (commercial mass), an adjustment for air buoyancy must be made: the standard density (kg/m3) is reduced by the air buoyancy correction value of 1.1 kg/m3, and then multiplied by the standard volume to obtain the product’s mass (m), as shown in equation (2). m = V20 × (ρ20 – 1.1)…………………(2) 1.1.3 Example of calculating the quantity of product: For a certain product, the temperature of the oil being transported is 40°C, and its volume is 1240.62 m3. The apparent density of this product at 40°C, as measured using an oil densitometer, is 753.0 kg/m3. The mass of the oil to be transported can be calculated using this value. Given the apparent density of the product at a test temperature of 40°C, which is 753.0 kg/m3, Table 59B is used to determine that ρ20 = 770.0 kg/m3. Using this standard density of 770.0 kg/m3 along with the oil transport temperature of 40°C, Table 60B is consulted to obtain VCF20 = 0.9775; thus, V20 = 1240.62 × 0.9775 ≈ 1212.706 m3. The mass of oil transported is then calculated as 1212.706 × (770.0 – 1.1) ≈ 932449.6 kg, or approximately 932.45 tons. When using the method of measuring oil volume by taking readings from oil tanks, in addition to adhering to GB/T 1885—1998, the following points should also be taken into account: To obtain more accurate values for the temperature and density of the oil inside oil tanks or pipelines, samples should be taken from the upper, middle, and lower parts of the tank, as well as at different times during oil transfer. These samples should then be mixed together, and their temperature, apparent density, and the temperature at which the apparent density was measured should all be determined ； Apparent density is the reading of a glass oil densitometer obtained at non-standard temperatures ； As required by the **quality control department, the oil tank inspection team regularly checks the size of the oil tanks or calibrates the oil transfer meters. 1.2 Differential pressure flow meter measurement method: For some materials, it is not possible to determine their quantity using tank gauging or the volume of oil transported; in such cases, flow meters must be used for measurement. For example, to save energy, thermal feeds such as atmospheric residue and vacuum residue are often used. In this case, only a flow meter can be used for measurement