Abstract: In order to assess the effect of organosilicon surfactant on aquatic organisms,the acute and joint toxicity of ethoxy modified trisiloxane (JIERUN) and siloxane compound (High-Speed) with three pesticides were studied using zebrafish (Brachydanio rerio) as test organism by semi-static method.The results showed that "JIERUN" and "High-Speed" were middle and low toxicity to zebrafish,respectively.The Co-Toxicity Coefficient (CTC) of "JIERUN" with fipronil,indoxacarb and acephate to zebrafish was 139.52,107.24 and 165.65,respectively,so the joint action was synergistic,additive and synergistic,respectively.The CTC of "High-Speed" with fipronil,indoxacarb and acephate to zebrafish was 111.36, 48.26 and 80.08 respectively,so the joint action was additive,antagonistic and additive,respectively.