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Double-suction centrifugal pumps are high-flow water pumps; therefore, it is necessary to adjust their flow rate. When making such adjustments, there are certain issues and methods that we need to take into account. Because improper adjustment methods have a serious impact on both the resulting performance and the efficiency of the pump. This article mainly summarizes and analyzes three effective methods for adjusting the flow rate of double-suction centrifugal pumps. Changing the pipeline characteristic curve: The simplest way to adjust the flow rate of a split-case pump is by controlling the opening degree of the outlet valve of the pump. Essentially, this involves changing the position of the pipeline characteristic curve in order to alter the operating point of the split-case pump. Changing the characteristic curve of a centrifugal pump: According to the law of proportionality and the law of modification, two methods can be used to alter the characteristic curve of a double-suction centrifugal pump – by changing its rotational speed or by modifying its structure (such as by reducing the outer diameter of the impeller). These methods enable the adjustment of flow rate (while also changing the head pressure). However, for pumps that are already in use, it is not convenient to modify their structure. Moreover, such structural changes reduce the versatility of these pumps; although it may be economical and convenient to adjust the flow rate in some cases, this approach is rarely used in production. Here, only the method of adjusting flow rate by changing the speed of the centrifugal pump is analyzed. Analysis shows that when the speed of the double-suction centrifugal pump is changed in order to adjust the flow rate from Q1 to Q2, the speed of the pump (or the speed of the motor) decreases from n1 to n2. At this speed of n2, the performance curve Q-H of the pump intersects the pipeline performance curve He=H0+G1Qe2 (which remains unchanged) at point A3Q2, H3; point A3 represents the new operating point after flow rate adjustment through speed control. This adjustment method offers significant, rapid, and safe results; it can extend the service life of double-suction centrifugal pumps and save energy. Additionally, operating at a lower speed helps to reduce the NPSHr of these pumps, keeping them away from the cavitation zone and thereby decreasing the likelihood of cavitation occurring. The disadvantage is that changing the pump’s speed requires using frequency conversion technology to adjust the speed of the prime mover (usually a motor); the principle behind this is complex, the investment required is high, and the range of flow rate adjustment is limited. Series and parallel operation modes of double-suction centrifugal pumps: When a single double-suction centrifugal pump is not sufficient to meet the transportation requirements, these pumps can be operated in parallel or in series. By connecting two identical double-suction centrifugal pumps in parallel, the head change is minimal, but the total flow rate of delivery increases; the overall efficiency of the parallel pumps is the same as that of a single pump ； When double-suction centrifugal pumps are connected in series, the total head increases while the flow rate remains roughly the same; the overall efficiency of the series-connected pumps is equal to that of a single pump.