Objective:To observe the effects of 5-aza-2′-deoxycitydine (5-aza-CdR) on the proliferation and transcription of tumor suppressor gene GSTP1 and RASSF1A in prostate cancer cell line PC3. Methods: The status of 5′CpG island methylation of RASSF1A and GSTP1 genes in PC3 was analyzed by methylation specific PCR (MSP) before treatment with 5-aza-CdR. RASSF1A and GSTP1 mRNA were quantified by real-time PCR during the demethylation process by 5-aza-CdR. MTT assay and flow cytometry were used to examine the proliferative activity of PC3 cells before and after 5-aza-CdR treatment. Results: The 5′CpG island methylation of RASSF1A and GSTP1 genes were detected in human prostate cancer cell line PC3. Compared with control group, RASSF1A and GSTP1 mRNA expression had no significant change 24 h after culture with 5-aza-CdR; their expression was up-regulated 48 h after cultured with 5-aza-CdR, with significant difference found between 5 μmol/L and 10 μmol/L 5-aza-CdR groups. Compared with control group, the expression of RASSF1A and GSTP1 mRNA was significantly increased 72 h after cultured with all concentrations of 5-aza-CdR. MTT assay and cell cycle examination indicated that exposure to 5-aza-CdR for 24 h and 48 h resulted in no obvious growth inhibition and cell cycle change; exposure to 5-aza-CdR for 72 h induced significant growth inhibition (P<0.05) and cell cycle change (P<0.05); and cells were arrested at G0/G1 phase. Conclusion: The 5′CpG island methylation of RASSF1A and GSTP1 genes is probably responsible for RASSF1A and GSTP1 silencing in PC3 cells. 5-aza-CdR can inhibit the proliferation of PC3 cells, disturb the cell cycle, and elevate transcription of GSTP1 and RASSF1A.