Abstract: Exploration practice in the Pearl River Mouth Basin suggests that the distribution of commercial oil and gas discoveries follow a pattern of “oil in north and gas in south”. With the progress in middle and deep exploration in the shallow water area, the first large-scale condensate gas reservoir was discovered in Mesozoic buried hills and Paleogene system of the Huizhou 26-6 structure in the Zhuyi Depression of the Pearl River Mouth Basin, which has raised people's attention to the natural gas resource potential in the shallow water area of the Pearl River Mouth Basin. In order to objectively and effectively evaluate the hydrocarbon potential of oil-type source rocks in shallow water area of the Pearl River Mouth Basin, the semi-deep lacustrine dark mudstone sample (Type Ⅱ₁) of the Wenchang Formation in the Huizhou 26-6 was selected to conduct the thermo-compression simulation experiment under a semi-open system. The model of hydrocarbon generation and expulsion are analyzed synthetically with the hydrocarbon potential of the oil-type source rocks, based on the analysis of the peak stages of hydrocarbon generation and the study of oil and gas production rates at different evolutionary stages for the oil type source rocks in the Huizhou 26 sag. In addition, the forming conditions of Huizhou 26-6 oil and gas field are investigated from the aspects of thermal evolution of source rocks, gas potential of source rocks and dominant convergence direction.