Abstract: OBJECTIVE: To study the reproductive toxicity of cypermethrin exposure on Caenorhabditis elegans and explore the feasibility of using Caenorhabditis elegans as a model organism in reproductive toxicology. METHODS：L4 N2 hermaphrodites were exposed to cypermethrin at 0.08、0.8 and 8.0 mg/L for 24，48，and 72 h. RESULTS：After exposure of 24 h，there was no significant change in the endpoints observed. After exposure of 48 h，together with the decrease in brood size，decreased relative length of secondary-lateral seminal vesicle oocyte and the number of egg in utero，reduced rate of egg-laying were observed in nematodes exposed to cypermethrin at certain experimental concentrations. After exposure of 72 h，significant decreases in brood size and relative length of secondary-lateral seminal vesicle oocyte were observed at 0.8 and 8.0 mg/L cypermethrin groups. CONCLUSION：Cypermethrin reduced the brood size through impairing the development of oocyte and egg. Meanwhile，Caenorhabditis elegans was sensitive to the exposure of cypermethrin and can be recommended to be used as a model organism in the field of reproductive toxicology.

Key words: cypermethrin, Caenorhabditis elegans, reproductive toxicity, reproductive capacity