In order to study the toxic effects of L7 lyophilized powder of extracellular active components (L7-LPEAC) – extracted from the algicidal bacteria L7 – on the aquatic system, Brachydanio rerio were exposed to L7-LPEAC in five different concentrations for a period of 96 hours. The results showed that the 96 h-LC50 is 0.85 g/L, thus the safe concentration is 0.09 g/L. Based on this, four L7-LPEAC concentrations (0.06 g/L, 0.09 g/L, 0.13 g/L, 0.18 g/L) were prepared with the same logarithmic distance, and a 20-day sub-acute toxicity test was carried out. The SOD and ATPase activity in the liver and gill of Brachydanio rerio was measured every 5 days. The results showed that with the increase of L7-LPEAC concentration, the SOD activity decreased significantly (P<0.05), both in liver and gill. Exposed over 10 days, the ATPase activity had little change when the concentration of L7-LPEAC was less than 0.09 g/L; and decreased significantly (P<0.05) when the concentration of L7-LPEAC was above 0.09 g/L.