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In the corrosive environments of oil and gas fields with high sulfur content, H2S gas is widely present in key processes such as extraction and processing, causing severe corrosion damage to stainless steel materials. Over the years, numerous studies have been published on the pitting problem of stainless steel in Cl- corrosive environments containing large amounts of H2S. When the H2S partial pressure is increased to 100 kPa, pitting begins to occur in stainless steel. As the H2S partial pressure continues to rise, the pitting potential of stainless steel decreases significantly, increasing its susceptibility to pitting. This indicates that the presence of H2S promotes the nucleation and growth of pitting in stainless steel. In oil and gas field environments, the presence of H2S can make 316L stainless steel more sensitive to critical pitting temperature; sulfur ions and chloride ions work together to penetrate the passivation layer on the surface of the stainless steel, thereby significantly reducing its corrosion resistance. The effect of H2S partial pressure on the pitting behavior of stainless steel was studied in a NaCl solution with a Cl- mass concentration of 15,000 mg/L. It was found that increasing the H2S partial pressure leads to a reduction in the thickness of the passive film on stainless steel, thereby decreasing its corrosion resistance. This further confirms that the synergistic effect of H2S and Cl- promotes the occurrence and progression of pitting in 316L stainless steel. In an 80°C aqueous solution containing H2S-Cl-, the passivation region of the polarization curve of 316L stainless steel disappears; simultaneously, the pitting potential decreases, the pitting current density is approximately 0.9 A/cm2, and the characteristic frequency of pitting increases. The surface passivation film dissolves, indicating that saturated H2S accelerates the pitting process in 316L stainless steel. Therefore, in oil and gas field environments, the presence of H2S can lower the pitting potential of stainless steel in Cl- containing solutions, causing the passivation film on the surface of the stainless steel to dissolve and thereby greatly promoting the formation and progression of pitting in stainless steel.