In the process of crude oil production，the H2S maybe release from the crude oil with the change of system temperature and pressure，resulting in potential safety hazards. At present，steam injection thermal production mode will aggravates the harm of H2S. The H2S release in an extraction liquid or the corresponding crude oil of Shengli oilfield after treatment at different temperatures was investigated and H2S production mechanism was mentioned. The crude oil or extraction solution was placed in an autoclave for high temperature treatment，then cooled to 50℃ to extract gas samples，and the gas samples was analyzed by gas chromatography. It was found that after 330℃ high temperature treatment，the H2S release from extraction liquid was less than that from the corresponding crude oil. Furthermore，the H2S release values of the crude oil treated at 200℃ or 85℃ were similar to each other，and the H2S release values were relatively large. The sulfur in released H2S reached up to 32.3% or 34.5% of the sulfur in the treated crude oil. Moreover，the study indicated that the main source of H2S released in the experiment was the H2S dissolved in crude oil. As crude oil coexisted with the formation water，some H2S dissolved in the formation water and reduced the H2S release.