In this study CO and CH4 molecule coadsorbed on the most stable structure of metal atom (Ni, Ag, Au, Rh, Zn, Pt) doped SnO2 (110) surface has been studied with the first principle methods. The formation energy calculation shows that the Au/SnO2 (110) surface is the most stable structure. We research the adsorption energy, bond length, bond angle, density of states, electron population and charge density difference of gas molecule adsorbed on Au/SnO2 (110) surface, which shows that Au/SnO2 (110) surface have excellent CO and CH4 adsorption performance. The stable adsorption of double CO on Au/SnO2 (110) surface shows that Au doping has practical value. The search of CO and CH4 coadsorption on Au/SnO2 (110) surface shows that the adsorption performance of CO on Au/SnO2 (110) surface was stronger than CH4 molecule. Our research indicates that Au/SnO2 is a potential CO sensor material.