Colorectal cancer(CRC)accounted for the largest number of new cases of cancer in 2018. CRC is caused by a multifactorial disease process including disruption of the circadian rhythm. Period 1(PER1),as one of the circadian genes,has a role in the cell cycle as well as influence on the cancer process. In this research,we investigate the association of PER1(rs3027188) polymorphism and susceptibility to CRC in conjunction with gender and smoking status. This research was a case-control study in the Japanese population which included 121 CRC patients and 197 noncancerous clinical controls. Genomic deoxyribonucleic acid(DNA)was extracted from peripheral blood lymphocytes. The analysis to detect single-nucleotide polymorphisms( SNPs)in PER1(rs3027188)used polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP). Overall,there was no significant association between PER1(rs3027188)and CRC. When stratified by gender and smoking status,the results indicated that,compared with the C/C genotype,the G/G genotype among females was significantly less common in the cancer cases than in the controls(adjusted ORs: 0.19[95%CI: 0.04-0.95]). A significant association was found between the G allele of PER1(rs3027188)and reduced risk of CRC in females,while smoking had no association with PER1(rs3027188)in CRC.