Diapirs are mainly secondary diapirs resulted from fault activity. But there are more syngenetic diapirs in Niger Termit Basin because early faults developed poorly. Through experimental simulation，the formation mechanism of mud diapirs in study areas is that the plastic mudstone was compressed by regional stress field which was the active force and warped up while two sides of the mudstone were loaded unevenly. According to the type of force and structural position，the mud diapirs in this area were divided into three types：faulted slope-extrusion diapir，low uplift-induced tension-differential loading diapir and sag-differential loading diapir. Impacts of diapir on hydrocarbon accumulation were mainly concluded as follows：①Uncompacted mudstone with high pressure has hydrocarbon generation potential，and the hydrocarbon will be generated after they reach into hydrocarbon generation threshold；②Diapirs penetration could improve the ability of oil and gas vertical migration and produce micro-cracks to make high-pressure fluid discharge easy；③Traps formed by diapir penetration are the anticline trap at the top of diapir and the lithologic trap at the sides of diapir；④Conditions of sands at the middle of slope near hydrocarbon-generation sag are superior to hydrocarbon accumulation，and the trap formed in this diapir penetration area is the favorable hydrocarbon accumulation zone. Exploration examples show that all wells drilled in the Cretaceous and basement near Moul sag are successful in oil test in the east faulted slope where diapir penetration developed the most.