Abstract: In this paper, adult zebrafish (Brachydanio rerio) which was recommended by the ISO standardization for testing fish toxicity was exposed to 10 kinds of chloro-benzene and alkylphenolic compounds. Their toxic effects were assessed in the toxicity test. Through multi-stepwise regression in SPSS 13.0 with the toxicity data (-lg LC₅₀) and the molecular parameters (²X^V, lg P), two regression equations were obtained.The results showed that there was significant linear relation between chloro-benzene toxicity and ²X^V as well as alkylphenol toxicity and lg P. Furthermore, their toxicity mechanisms were discussed briefly.