Abstract: Chezhen sag, located at the northwest of Jiyang Depression, is a Mesozoic and Cenozoic rift basin. Three series of source rocks such as Es4, Es3 and Es1 of Eogene were well developed in this sag. Oil-gas reservoir condition is multiform including carbonatite, clasolite as well as magmatite, metamorphite and fractured mudstone. Chezhen sag has multi-combination of reservoir-cap, multi-type of trap, and multi-period of hydrocarbon migrating and gathering which match with the trap forming, so it has favorable condition to form oil-gas pools.The unexplored petroleum resource of Chezhen sag is over 4.6×10⁸t. Therefore, Chezhen sag has enormous exploration potential. It is considered that the lower exploration area and new oil-bearing series are the major exploratory directions.