Prion leads to fatal transmissible spongiform encephalopathies. Cellular prion protein (PrPC) is necessary in prion disease. At present, it is demonstrated that PrPC plays a protective role in several carcinomas, such as gastric and breast cancer. We designed four 19-nt siRNAs according to cDNA sequence of human PrPC and constructed retrovirus-based RNAi vectors. We evaluated the inhibitive effect of these sequences on HuPrPC (human PrPC) and selected out three sequences with stable and efficient inhibition. And the efficiency of si626 reached more than 85%, which effect was significant. Next, we performed cell invasion assays of PC3M-si292 and PC3M-si626 in which PrPC was inhibited. And it showed that the cell invasive ability decreased in PrPC knock-down cell lines. This will make preparations for the further research on gene therapy of prion diseases and PrPC related carcinoma treatment and PrPC could be considered as a potential therapeutic target molecule in prostate cancer treatment.