Abstract: The current study investigated the safety and the anthelmintic efficacy of two common disinfectants, sodium hypochlorite and chlorine dioxide using G. kobayashii parasitizing goldfish (Carassius auratus). The result showed that the average survival time of Gyrodactylus kobayashii was less than 2h in vitro when the effective concentrations of sodium hypochlorite and chlorine dioxide were equal or greater than 0.2 and 0.15 mg/L, whereas 20.8h in the control group. When the effective concentration of chlorine dioxide was not less than 0.15 mg/L, more than 70% of the worms were dead and became black, the worms remain transparent but die in lower chlorine dioxide groups. The anthelmintic efficacy in vivo increased along with rise of the drug concentrations and almost reached 100% when the effective concentrations of sodium hypochlorite and chlorine dioxide were 0.2 and 0.5 mg/L, respectively. When the effective concentration of chlorine dioxide was 0.6 mg/L, white floccule was observed in the aquaculture water. The anthelmintic efficacy in vivo of NaClO was better than ClO2. The safe concentrations of sodium hypochlorite and chlorine dioxide to goldfish were 0.18 mg/L and 0.48 mg/L, respectively, which were slightly lower than the minimum concentrations completely killing G.kobayashii in vivo. Hence, it should be cautious to use sodium hypochlorite and chlorine dioxide to control Gyrodactylus in goldfish, but it need further investigation whether this disinfectants could be used for other fish in controlling Gyrodactylus.