AIM: To observe the lesions of Oncomelania hupensis after treatment with the seed of camellia sinensis (SCS). METHODS: The tissue of the hepatopancreas and genital system in normal and SCS-treated Oncomelania hupensis were observed by transmission electron microscopy TEM. RESULTS: Aften the Oncomelania hupensis snails were treated with SCS (8 μg/ml) for 24 h, cloudy swelling and coagulating necrosis of parenchyma cells of the hepatopancreas, coagulating and dissolving changes in spermatogonia, cloudy swelling of the spermid membrane with isolating internal substance, aggregation of mitochondria, cloudy swelling of ova, deformity of ovum membrane and rupture of follicles were observed by TEM. CONCLUSION: SCS could damage the hepatopancreas and genital system of Oncomelania hupensis.