Objective:To explore the methylation status and expression of Ras association domain family 1A (RASSF1A),and the possible effect between promoter aberrant methylation and the pathogenesis of pancreatic cancer. Methods: We detected the methylation status of RASSF1A promoter CpG island (CGI) in pancreatic cancer cell line PANC-1,normal pancreatic tissue and 1 pairs of pancreatic tissues(cancer and para-cancerous tissue) by using bisulfite genomic sequencing PCR (BSP) combined with TA clone for sequencing. The methylation rate of RASSF1A in PANC-1 was compared before and after treatment of the inhibitor of DNA methyltransferase (5-aza-2-deoxycitydine,5-aza-dC),and reverse transcription PCR(RT-PCR) were used to explore mRNA expression of the RASSF1A gene. Results:The average methylation rate of RASSF1A promoter CGI was 100.00% in PANC-1,1.79% in normal pancreas,93.75% in para-cancerous tissues,and 100.00% in cancer tissues. The methylation rate of para-cancerous or cancer tissue was higher than that of normal pancreas(P < 0.01),but there was no significant difference between para-cancerous tissues and cancer tissues(P > 0.05). After the treatment of 5-aza-dC,the methylation rate in PANC-1 was decreased to 88.89%(P < 0.05),but the mRNA of RASSF1A had no change. Conclusion: This promoter hypemlethylation is correlated with RASSF1A gene expression in pancreatic cancer cell line PANC-1 and pancreatic tissues,and plays a key role in RASSF1A silencing. Aberrant hypermethylation of RASSF1A could probably become early diagnosis index and treatment target of pancreatic cancer.