Based on the research of Lenghu No.3- 5 structural belt, it is concluded that hydrocarbon accumulation of this structural belt is mainly affected by the following factors: ① the residual Lower Jurassic located in the western Lenghu area provides material foundation for the hydrocarbon accumulation of this structural belt; ② the Lower Jurassic which acts as the hydrocarbon source rocks was buried properly, and there exists an ideal matching of structure configuration and large scale hydrocarbon generation stage; ③ tectonic evolution of the residual hydrocarbon-generation depression makes Lenghu structural belt become the advantageous structural belt; ④ the tectonic setting of Lenghu structural belt has the characteristics of higher in north and lower in south, which results in that the Lenghu No. 3- 4 structural belt is better than Lenghu No. 5 structural belt in reservoir formation. It is indicated that Lenghu No. 3- 5 structural belt is still the advantageous direction of oil and gas exploration in this area.