In the exploration area of marine sedimentary sequences, two sets of good source-reser- voir-cap assemblages develop under Middle Cambrian Qinjiamiao subsalt strata. By analysis of the subsalt characteristics and distribution of the source rocks, reservoirs and cap rocks, it is indicated that the Upper Sinian Doushantuo shale and Lower Cambrian Shuijingtuo shale are good source rocks, and the Upper Sinian Dengying carbonate rock and Lower Cambrian Shilongdong carbonate rock can provide good reservoir conditions. The Middle Cambrian Qinjiamiao salt rock and the Lower Cambrian Shipai and Tianhe argillaceous rocks also play the good role of regional cap rocks that seals hydrocarbon under them. It is suggested out that the favorable exploration areas are in Shizhu Synclinorium, the west part of Lichuan synclinorium and Yichang Stable Zone.