To investigate the effects of warm waste water from nuclear power plants on the long-term stress of aquatic animals, the influence of free residual chlorine on the oxidative pressure of Tegillarca granosa under different temperature conditions were studied through laboratory simulation. Water temperatures were set as 19 and 29 °C, and two different gradients of free residual chlorine concentration were set as 0.33 mg/L and 6.66 mg/L. The results showed that: ① water temperature can significantly affect the ROS level. The higher the temperature, the higher the ROS level. ② the ROS level and DNA damage of T. granosa in 0.33 mg/L group were increased significantly on day 20, which were 2.2, 2.9 times and 1.8, 2.2 times higher than those in the control group at 19 and 29 °C, respectively; the cell activity, ATPase activity and SOD enzyme activity decreased significantly; the ROS level in the 6.66 mg/L group increased significantly on day 20, which was 6.2 and 3.6 times higher than that in the control group at 19 °C and 29 °C, respectively; the DNA damage increased; the cell activity, hemocyte phagocytosis rate and ATPase activity decreased; SOD enzyme activity decreased to the minimum value of (36.4±8.4) U/(mg prot) at 29 °C on day 20. ③ two-factor analysis of variance showed that water temperature and free residual chlorine had significant interaction on the parameters of ROS level, DNA damage, hemocyte phagocytosis rate and ATPase activity. The results indicate that free residual chlorine can significantly increase the ROS level and the DNA damage of T. granosa. The combined exposure of water temperature and residual chlorine, which caused greater stress pressure on T. granosa, affected the physiological processes related to oxidative stress. In the residual chlorine discharge area, greater oxidative stress would be faced by T. granosa in summer than in winter. This study can give a reference for studying oxidative stress toxicity of marine organisms exposed to warm water combined with residual chlorine, and provide scientific basis for ecological risk assessment.