Abstract: As acommon environmental pollutant, phentriazophos is the kind of organophosphorous pesticide which always endangers the safety of aquatic organism. This research is due to find out the acute toxicity of phentriazophos on five species of genus Anguilla elver. The results showed that the five species' reaction to phentriazophos were similar but there were differences among the lethal concentration range. The order of acute toxicity was Anguilla anguilla＞A.mormorata＞A.japonica＞A.rostrata＞A.bicolor pacifica; the safe concentration of phentriazophos to these species were: 1.2210-4, 4.1210-4, 6.1610-4, 2.2410-3and7.5310-3 mgL-1, respectively. The endurance ability of A.rostrata and A.bicolor pacifica was stronger than that of the other three species. The time effect and concentration effectof this experiment were significant, which meant that the mortality increased accordingly with increasing concentration of phentrazophos during the same experimental period, and it alsoincreased with the elapsed experimental timewithin the same concentration of phentriazophos. The toxicity of phentriazophos to the five species of genus Anguilla elver was all severe.