〔Abstract〕 Objective To investigate the effects of 3 types of trihalomethanes(THMs), the by-products in treatment of drinking water disinfection, on the development and reproductive capacity of germ cells ofCaenorhabditis elegans.Methods Tribromomethane( TBM), trichloromethane( TCM) and triiodomethane( TIM), 3 types of THMs were selected and wild typeCaenorhabditis eleganswas used as a model to detect germ cell apoptosis, oocyte number and the final brood size after exposure to different concentrations of THMs.Results The results of germ cell apoptosis showed that the exposure to 50 μmol/L TCM and TIM caused elevated levels of germ cell apoptosis in a dose-dependent manner. Oocyte counting results showed that exposure to 50 μmol/L all three THMs significantly reduced the number of oocytes. The brood size results showed that only 50 μmol/L TIM exposure significantly decreased the brood size of nematodes.Conclusion THMs showed negative impacts on the reproductive system of Caenorhabditis elegans, and the toxicity is related to the halogenated elements of THMs.