Abstract: With the development of oil generating theory and exploration technique, studying distribution of Mesozoic Era sedimentary stratum is demanded in west depression belt of the East China Sea shelf basin. On the basis of intermediate-acidity magmatic rock with magnetism and the density difference of Mesozoic Era sedimentary stratum and upper layer and down layer, studying distribution of Mesozoic Era sedimentary stratum and intermediate-acidity magmatic rock is possible. Using 2.5D gravity-magnetic man-computer interactive formal-inversion calculation, geological structures of four profiles are studied. The result is a condition of restriction. Using the technique of wavelet analysis and polarization, plane's gravity-magnetic results are processed and comprehensivly studied. Distribution of Mesozoic Era sedimentary stratum and intermediate-acidity magmatic rock are studied. In the text, Mesozoic Era sedimentary stratum is considered as continual distribution in west depression belt of the East China Sea shelf basin, but it is separated at 30°N. Mesozoic sediment thickness is greater than 3km is the basic condition to form oil-gas perspective areas.