Abstract: A number of wells in Qiudong subsag of Taibei sag of Tuha Basin have obtained high-yield oil and gas flow in Sangonghe Formation of the Middle-Lower Jurassic Shuixigou Group, showing a good hydrocarbon exploration prospect of the deep intra-source tight sandstone in the subsag area. To make clear the petroleum geological conditions of tight sandstone from Shuixigou Group in Qiudong subsag and comprehensively evaluate the exploration prospects of Shuixigou Group in Tuha Basin, based on the drilling knowledge obtained from new boreholes, this paper systematically summarizes the favorable accumulation conditions of Qiudong subsag, and points out the next exploration direction. (1)Qiudong subsag suffered from multiple tectonic movements and developed three tectonic zones, namely southern slope, central subsag, and northern slope. Among them, the central subsag was tectonically stable, which was conducive to hydrocarbon preservation in the multi-stage superimposed basin. (2)Shuixigou Group in Qiudong subsag developed two sets of coal-measure source rocks in Badaowan Formation and Xishanyao Formation respectively, as well as lacustrine argillaceous source rocks in Sangonghe Formation. The dominant kerogen types were Ⅱ₂—Ⅲ and in mature evolution stage. (3)Shuixigou Group in Qiudong subsag developed bidirectional braided river delta sedimentary system to the south and north. The sand-bodies in the subsag area developed well and effective reservoirs developed even below 5 000 m under the control of such factors as favorable facies, dissolution, overpressure, and fractures. (4)By comprehensively analyzing the exploration potential of tight sandstone gas from Shuixigou Group in Taibei sag, it showed that the superposition of large coal-measure source rocks and braided river delta front sand-bodies were developed in all three subsags (Shengbei subsag, Qiudong subsag and Xiaocaohu subsag). Five main fan bodies, namely Pudong, Hongbei, Lingbei, Qiudong, and Gebei, can be selected from Sangonghe Formation with the favorable exploration area of 1 090 km², evaluated natural gas resource of 5.29×10¹²m³, and petroleum resource of 5.2×10⁸t. The great resource potential shows that the sag area in Tuha Basin has a good exploration prospect.