Phytochelatins (PCs) play an important role in heavy metal resistance and accumulation. To reduce the accumulation of cadmium (Cd) in rice seeds, the expression of phytochelatin synthase (PCS) gene OsPCS1 was suppressed by RNA interference (RNAi). A hairpin construct of a PCS fragment was designed in the pRNAi-OsPCS1 under the control of ZMM1, a seed-specific promoter from maize. The construct was introduced into rice (japonica) through Agrobacterium tumefaciens. The RNAi rice plantlets were selected and cultivated in pots exposured to 10 mg/kg Cd. The transcriptional level of OsPCS1 declined in seeds of some RNAi rice compared to the wild type. As a result Cd accumulation was reduced by about half in the seeds of RNAi rice. As expected, no apparent difference of growth appeared between RNAi and wild-type plants. The results suggest that this new approach can be used to control heavy metal accumulation in crops.