During the reactor operation, dissolved oxygen generated by water radiolysis is an important factor in influencing corrosion resistance of zirconium alloy. CZ2, a zirconium alloy independently developed by China General Nuclear Power Group, has shown promising performance in reactor. This study investigated the impact of dissolved oxygen on the corrosion behavior of CZ2 alloy cladding and Zr–Nb alloy cladding through weight gain analysis and visual appearance assessment. Additionally, the effects of varying oxygen concentrations on CZ2 alloy were further analyzed via hydrogen content measurements and fractural surface morphology observations. Corrosion tests were conducted in a circulating autoclave loop system under a dissolved oxygen environment. After exposure to a 300 ppb dissolved oxygen environment for 180 days, the weight gains of CZ2 alloy cladding and Zr–Nb alloy cladding were recorded at 61.51 mg/dm2 and 68.47 mg/dm2, respectively. Results indicate that dissolved oxygen slightly increases the weight gains of both CZ2 and Zr–Nb alloy cladding. Furthermore, CZ2 alloy demonstrates superior corrosion resistance compared to Zr–Nb alloy in both deaeration and dissolved oxygen environments. Fractural surface observations reveal that the oxide film of CZ2 alloy in the dissolved oxygen environment seems to have more pores and micro-cracks, which may be associated with its relatively lower corrosion performance in such conditions.