Abstract: The paper aims to study the effects of concentration of Cu2+ in the recirculating aquaculture system on the purification efficiency of the system. Adding Cu2+ through the generator in the recirculating aquaculture system, we evaluated the germicidal efficacy by monitoring water quality and the health of zebrafish. The results showed that: the increase speed R2 of Cu2+ in the generator was 0.9942 with better stability; after 24 h, when the concentration of Cu2 + got to 0.76 mg/L, the zebrafish began to die; in the same concentration, the lower the temperature, the higher the zebrafish’s tolerance to Cu2 + ; in the same temperature, the zebrafish could die faster with the increasing concentration of Cu2+; in the safe concentration (the concentration of Cu2+ was 0-0.23 mg/L), the suitable breeding temperature was (26±2)℃ and the Cu2 + could inhibit the bacteria effectively when the concentration was 0.14-0.226 mg/L. We make a 20-day zebrafish fishing test to verify the results, the concentration of nitrate nitrogen, nitrite nitrogen, TAN change similarly when the concentration of Cu2 + get higher; the concentration of nitrate nitrogen, nitrate nitrogen, TAN and the total number of bacteria keep in a stable state when the concentration of Cu2+ is 0.1-0.2 mg/L and the breeding temperature is (26±2)℃, and this condition is beneficial for the growth of zebrafish.