To improve the performance of CO2 photoreduction to CO, S-scheme AgBr/BiOBr heterojunctions with strong interfacial interactions were prepared using a simple in situ hydrolysis strategy by regulating the stoichiometric ratio of BiOBr and AgNO3. Furthermore, the synthesized AgBr/BiOBr heterojunctions were subjected to microstructure analysis and electrochemical properties testing. The experimental date show that AgBr/BiOBr heterojunctions, which have tight interfacial contact characteristics, boost visible light utilization and facilitate the separation and shift of photogenerated carriers, leading to strong CO2 redox capability. Among the AgBr/BiOBr heterojunctions, the AB-2 specimen has the best selectivity for the product CO. The rate of CO2 photoreduction to CO for AB-2 is 25.36 μmol·g-1·h-1, which is about 2.48 and 11.91 times higher than those of acquired BiOBr and AgBr, respectively. After several cycles, it still exhibits high stability. Furthermore, the electric charge transfer and CO2 reduction mechanism for the S-scheme AgBr/BiOBr heterojunction were investigated. A promising method for the construction of efficient photoreduction CO2 catalyst is proposed in this study.