Objective: To inrestigate the association between thymidine phosphorylase (TYMP) polymorphisms and efficacy of postop-erative capecitabine-based adjuvant chemotherapy in colorectal cancer (CRC) patients. Methods: Two hundred and thirty-five patients with colorectal cancer who received surgical treatment and adjuvant chemotherapy between January 2010 and December 2016 from People's Hospital of Zhengzhou, were included in this study. Peripheral blood and postoperative tissue specimens of the CRC patients were collected for genotyping polymorphisms and measuring TYMP mRNA expression, respectively. The correlation between the poly-morphisms and efficacy of postoperative chemotherapy in CRC patients was analyzed. Results: The prevalence of 5633C>T in TYMP gene among the CRC patients was as follows: CC genotype, 149 cases (63.40%); CT genotype, 73 cases (31.06%); and TT genotype, 13 cases (5.54%); the minor allele frequency of 5633C>T was 0.21. Survival analysis of the patients revealed that the median overall sur-vival (OS) of patients with the CT/TT genotype and those with the CC genotype was 5.9 and 4.5 years, respectively; the result was sta-tistically significant (P=0.009). Following adjustment in multivariate Cox regression analysis, the CT/TT genotype was found to be an in-dependent favorable factor for OS (HR=0.67, P=0.015). Additionally, of the 87 postoperative tissue specimens, results show that the levels of TYMP mRNA in cancer tissues of patients with the CT/TT genotype were significantly higher than those with the CC genotype (P=0.019). Conclusions: TYMP mRNA expression may be influenced by the 5633C>T polymorphism, making CRC patients benefit from capecitabine treatment.