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 (2XV, lg P), two regression equations were obtained. The results showed that there was significant linear relation between chloro-benzene toxicity and 2XV as well as alkylphenol toxicity and lg P. Furthermore, their toxicity mechanisms were discussed briefly.