A large scale one-pot coprecipitation method is developed for synthesis of ZnO/ZnGa2O4 heterojunction photocatalysts. XRD and Raman spectra show that ZnO and ZnGa2O4 are formed. SEM images indicate the particle size of ZnO/ZnGa2O4 heterojunction composites is about 20 nm. The HRTEM images show a close contact between ZnO and ZnGa2O4. The activities of photocatalysts are evaluated by photocatalytic degradation of methyl orange (MO) in the aqueous solution. The efficiency of MO degradation on the optimum photocatalysts ZnO/ZnGa2O4-0.2 shows about 82% in 70 min, which is greatly higher than that of ZnO ( 6%) and ZnGa2O4 (47%). It is proposed that the heterojunctions between ZnO and ZnGa2O4 promote the charge separation and is responsible for the improved photocatalytic activity. The synthetic method of ZnO/ZnGa2O4 heterojunction has potential commercial value and can be applied to other semiconductors heterojunctions with similar structure of X/XY. (C) 2014 Elsevier B.V. All rights reserved.