The Fengcheng Formation in Mahu Sag is currently the oldest known alkaline-lacustrine deposition in China, with well-developed high-quality lacustrine source rocks. These source rocks from the Fengcheng Formation play a crucial role as a material foundation for oil and gas production in the Junggar Basin. In order to understand the hydrocarbon generation evolution characteristics of source rocks, the WYMN-3 high temperature and high pressure semi-closed simulation experiment platform was utilized. This platform simulated the hydrocarbon generation process of source rock samples obtained from the Fengcheng Formation of Well Maye 1 in the Mahu Sag. The experiment yielded data on oil generation parameters, gas generation parameters, and the gas carbon isotope composition of source rocks. Subsequently, an analysis of the hydrocarbon generation evolution process of the source rocks was conducted. The results show that the mudstone of the P₁f₂ is dominated by oil generation and supplemented by gas generation in the process of heat evolution. At 350 ℃, the yield of expelled oil and residual oil peaked at 325.35, 239.45 mg/gTOC, respectively, and there is still oil generation potential in the high temperature stage (400 ~ 500 ℃). The gaseous hydrocarbon begins to gradually produce after 375 ℃, and its source is mainly the secondary cracking of oil. There is no Reversal phenomenon in the carbon isotope sequence of hydrocarbon gases. However, there is a Rollover phenomenon in the low temperature stage, 350 ℃ is the turning point, which is also the temperature point of the peak of oil generation. Based on the hydrocarbon yield, carbon isotope composition of gaseous hydrocarbons, and isomerization ratio of hydrocarbon gases, the hydrocarbon generation process of source rocks in the Fengcheng Formation can be categorized into four stages: initial kerogen cracking→kerogen cracking→oil cracking→oil and gas cracking.