Abstract: Diabase is widespread on the northern slope of the Gaoyou sag.The intrusion of diabase into the oil-and-gas-bearing basin may change the environment of oil and gas formation.This article discusses the relationship between diabase invasion and oil generation,migration and accumulation.It is suggested that diabase invasion may be favourable for the generation,migration and trapping of oil and gas.The mechanism for the formation of the complex fault block reservior is also discussed.