摘要： Textile and dye effluents have strong color, unstable pH and COD, a lot of inorganic salt, and high biotoxicity. It is difficult and inefficient to remove dyes from high‐saline wastewater by traditional methods. In this study, a simple synthetic CuO/CeO2 photocatalyst is used to achieve high efficiency photodegradation of methylene blue in high salt wastewater. The p‐type CuO/n‐type CeO2 heterojunction photocatalyst is synthesized by a modified hydrothermal‐calcination method. The XRD and XPS reveal the successful synthesis of CuO/CeO2 composite. The SEM and TEM images show that the sample consists of large amounts of well‐dispersed CuO nanosphere loading on the CeO2 layers. DRS exhibits the absorption band (about 510 nm) and the band gap energy (2.43 eV) of the CuO/CeO2 composite. Compared with pure CuO, CeO2, and TiO2 (P25), the prepared CuO/CeO2 can increase the mineralization rate of MB by 18.19%~33.74%. More than 80% of MB can be effectively removed in the wastewater containing 5~80 g/L NaCl with a wide pH value range of 2.11~9.02, and the degradation processes follow the pseudofirst‐order reaction kinetics. Active species trapping experiments confirm that the degradation of methylene blue is mainly attributed to hydroxyl radical; besides, O2?? and hole (h+) also play important roles. Chlorine ions have dual effects in photocatalytic reactions. This work could provide a new approach to construct new heterojunction photocatalysts and a deeper insight for the treatment of hypersaline dye wastewater.