A novel Ag/AgBr/Ga2O3 composite with heterojunction microstructure was synthesized by using chemical deposition followed by UV reduction method. High resolution transmission electron microscopy showed that Ga2O3 microparticles were tightly attached with Ag/AgBr to form a heterojunction. UV–vis diffuse reflectance spectra revealed that light response capability of Ga2O3 was enhanced significantly when combined with Ag/AgBr. The degradation efficiency of methyl orange within 30 min under UV light irradiation with Ag/AgBr/Ga2O3, Ag/AgBr and Ga2O3 were 89%, 74% and 48%, respectively. Ag/AgBr/Ga2O3 not only showed excellent photocatalytic activity under UV light, but also exhibited efficient photocatalysis capacity under visible light. Furthermore, the mechanism of charge separation in the heterojunction under UV light irradiation was proposed.