Abstract: Geologic investigation and petroleum exploration in our sea area indicate that various Mesozoic basins developed in shelf area are mainly structure-remain basin and faulted basin styles, and show definite petroleum exploration potential in Mesozoic basins,although petroleum geologic conditions are so complicated and more technical difficulties will be there. After some explorations and research works, East China Sea shelf basin shows Paleogene as an important explorating target, and besides, Mesozoic basin is also a indefeasible exploration field. On the base of the analysis of recently collected Mesozoic data, this paper describes basic geologic features of Mesozoic basin in the midwest shelf basin of East China Sea including geologic textures, structure types, strata distributions and facies charateristics and essential appraisement of petroleum geologic conditions indicates that Fuzhou depression located at the southern basin have developed mid-lower Jurassic petroleum system and middle-sized resources scale, which are commonly forecasted to form middle-small fileds and show definite explorating values.