The EC50 of our laboratory and commercial chlorine dioxide for grouper egg hatch ratewere 0.88 and 0.73 mg/l. The 24 hours LC50 of our laboratory and commercial chlorinedioxide for 1 day old grouper larvae were 0.66 and 0.65 mg/l. The 24 hours LC50 of ourlaboratory and commercial chlorine dioxide for postlarvae X of white shrimp were 1.96 and 2.85 mg/l.The degradation rate of chlorine dioxide was affected by salinity, total alkalinity and aeration. Nitrite could be oxidized by chlorine dioxide in different salinity water. But ammonia could not be oxidized by chlorine dioxide in fresh water, and ammonia in sea water could be oxidized by chlorine dioxide.