At room temperature, graphene has excellent electrical properties such as large molecular adsorption specific surface area, low noise and high carrier mobility. Compared with traditional inorganic oxide gas sensors, graphene gas sensors have the advantages of low operating temperature, low energy consumption and high recovery. This paper reviewed the research progress of two graphene gas sensors. Firstly, NO2 and NH3 graphene gas sensors were studied according to different gas selectivity. Then their sensitivity, gas response sensitivity and response time were analyzed and compared. This analysis and research work has certain reference value for the practical application and popularization of gas sensor.