Abstract: Prospecting evaluation of Tertiary source rocks in the Yinggehai Basin is in the exploration stage at present. According to regional geology, sedimentary and tectonic evolution features of Tertiary, seismic data, previous researches and the result of hydrocarbon-generating simulation experiments, source rocks in various horizons were analyzed, particularly the organic geochemical characteristics of Palaeogene source rocks. On the basis, this paper makes an intensive study on hydrocarbon source condition and thermal evolution of organic matter under the condition of HT and HP. The results have shown that Miocene marine mudstones are the main source rocks of shallow gas reservoirs and mid deep, as well as Eocene-Oligocene lacustrine mudstones and coals are important source rocks in the basin. Miocene marine source rocks containing Kerogen typeⅡ₂ and typeⅢ are widely distributed, and the maturity of organic matters is between mature and high mature phases for gas generation. Moreover, Eocene-Oligocene source rocks are mainly distributed in northwest and southeast of the basin, and the organic matter is the humic with high generation potential of hydrocarbon. Based on tectonic evolution characteristics and hydrocarbon source conditions, combining exploration achievements and comprehensive assessment of hydrocarbon accumulation area in recent years, the paper forecasts that, not only the Lingao inversion structures zone and the Lingao-Haikou-Changhua area are very important to the Tertiary oil-gas exploration, but also the Yingdong slope and the area beside the Qiongdongnan basin at the down throw side of No. 1 fault belt. What's more, the middle-deep structural traps under the condition of HT and HP in deep are very important for exploration of medium and large gas pools.