Abstract: In order to assess the toxic effects of chlorpyrifos to different life stages of fish, Chinese rare minnow(Gobiocypris rarus) was used as the test animal, and the acute toxicity as well as the toxic effects of chlorpyrifos on embryonic development of G.rarus were evaluated. The results showed that the 96 h-LC50 value of chlorpyrifos to embryos, larvae, juvenile and adult fish of rare minnow was 7.59 (5.14-9.86), 0.393 (0.326-0.447), 0.047 8 (0.038 2-0.054 9) and 0.027 2 (0.021 9-0.041 9) mg/L, respectively. The toxicity of chlorpyrifos to four different life stages of rare minnow as follows: adult fish> juveniles >larval fish> embryo. It shows that the most sensitive symptom was spinal deformity when exposed to chlorpyrifos. In addition, the embryos hatching rate of rare minnow was significantly promoted by chlorpyrifos in the concentration range of 6.13-35.8 mg/L at 48 h.