Abstract: A 96-hour acute toxicity test was carried out to study the effect of Hg²⁺ on 5 species of Anguilla elver (Anguilla japonica, A.anguilla, A.bicolor pacifica, A.mormorata, A.rostrata). Result indicates that 24 h LC₅₀ of Hg²⁺ is A.japonica(0.408 mg · L^-1)> A.anguilla(0.179 mg · L^-1)> A.rostrata(0.111 mg · L^-1)> A.mormorata(0.052 mg · L^-1)> A.bicolor pacifica(0.018 mg · L^-1).However, 48 h, 72 h and 96 h LC₅₀ of Hg²⁺ is A.japonica>A.rostrata> A.anguilla>A.bicolor Pacifica>A.mormorata. Generally, A.japonica and A.rostrata show better tolerance and Hg²⁺ should be restricted in aquatic water strictly.