Objective：To investigate the expressions and significances of circadian clock gene Per1 in patients with oral squamous cell carcinoma（OSCC）. Methods：Expressions of Per1 in 38 cases of buccal squamous cell carcinoma and the adjacent non-tumor tissues were examed by immunohistochemical SP method and Western blot method and the significances of Per1 were studied combined with the clinicopathological parameters. Results：Expressions of Per1 were significantly decreased in buccal squamous cell carcinoma tis－sues than in adjacent non-tumor tissues（P=0.025）. In buccal squamous cell carcinoma，expressions of Per1 were significantly higher in stageⅠ，Ⅱ period and T1，T2 grade than in stage Ⅲ，Ⅳ period and T3，T4 grade（P=0.007）（P=0.030），meanwhile the expressions of Per1 were significantly higher in group without lymph node metastasis than in group with lymph node metastasis（P=0.008）. Ex－pression of Per1 was in no correlation with patients’ gender，age and pathological grade（P >0.05）. Conclusions：Expression of Per1 may play an important role in the development，invasion and metastasis of patients with OSCC，and may provide a new way of thinking for OSCC diagnosis，prognosis assessment and treatment.