Abstract: As a unique Mesozoic sedimentary basin of marine and transitional facies in the eastern part of China, Sanjiang basin was intensely reconstructed by the tectonic movement at the end of early Cretaceous, thus its prototype basin is quite different with the present residual basin. The thermal evolution of organic matter was in mature to highly mature phases. The Upper Jurassic, Lower Jurassic and Tertiary source rocks were developed, thus hydrocarbon sources were relatively rich. Two groups of faults and unconformities, resulted from the multiphase tectonic movements and volcanic activities, acted as the favorable hydrocarbon migration pathways. There were several trap types and the formation time of which was relatively early and matched well with hydrocarbon generation and expulsion. Two different types of plays occur in the western and eastern parts with large exploration potentials.