Abstract: The controlling factors of hydrocarbon accumulation in the Lower Triassic Baikouquan formation of Wellblock MH-1 on the southern slope of Mahu sag are very complicated. Inverse oil-water relations of oil and gas zones located on the lower structural positions and aquifers located on the higher structural positions, unclear reservoir controlling factors and undefined reservoir forming rules are the bottleneck problems constraining petroleum exploration in the area. The distributions of main channels of fan body, facies boundary and subfacies of fan delta front are determined based on the detailed study on paleogeomorphology. The spatial distribution of good quality reservoirs are predicted by using pre?stack elastic parameter inversion. 5 period superimposed sand bodies with poor lateral connectivity developed in the Baikouquan formation of Wellblock MH?1 forms a lithological trap group. The SW trending reverse fault was the main path for primary oil and gas migration during the late Indosinian movement. A hydrocarbon accumulation model of “ one sand body is one reservoir” is established for the Baikouquan formation in Wellblock MH-1, the distribution of favorable accumulation area is predicted and breakthrough has been gained in the 2 appraisal wells, which can verify the model and provide theoretical guidance for further petroleum exploration in the wellblock