Objective：To investigate PCDH17 gene promoter methylation status and its impact on the transcriptional expression of PCDH17 in NPC （Nasopharyngeal carcinoma，NPC） cell lines.and to investigate the function of PCDH17 in nasopharyngeal carcino－ma. Methods：Semi-quantitative reverse transcription PCR （RT-PCR） and Methylation specific PCR（MSP） were used not only to de－tect transcription level and promoter methylation status of PCDH17 gene in five NPC cell lines，human laryngeal carcinoma cell line （Fadu），normal immortalized epithelial cell lines（NP69），but also after NPC cell lines were exposed to demethylating agent.The tu－mor-suppressive function of PCDH17 in NPC cancer was investigated further in vitro assays. Results：PCDH17 was not expressed in 5 NPC cell lines and in Fadu，but expressed in NP69.Demethylating agent could restore the expression of PCDH17 mRNA.The Cell function experiments suggest that PCDH17 could inhibit the cell colony formation and migration. Conclusion：The transcriptional in－activation in NPC cell lines is mainly caused by the DNA methylation.PCDH17 plays a role of tumor suppressor gene in NPC.