The high incidence and mortality of cancer threaten human health and lifespan. One-carbon metabolism is one of the important metabolic pathways involved in tumor pathogenesis. The effects of folate and homocysteine two key components of the one-carbon metabolism pathway have attracted the attentions of a large number of studies. Meanwhile multiple functional gene polymorphisms in the one-carbon metabolism pathway also play roles in carriers' susceptibility to cancers but this relationship is often modified by many confounders including nutrients in the one-carbon metabolism pathway. In addition other studies proved these gene polymorphisms are determinants of the sensitivity and toxicity to chemotherapy drugs thus genotype information may provide a basis for the selection and dose setting of clinical chemotherapy drugs. Some studies have found that these functional gene polymorphisms have potential value as prognostic predictors of cancer patients. In this review the research on these aspects is summarized. Nowadays "precision medicine and personalized treatment" has become an important trend in medical development studies on functional gene polymorphism in the one-carbon metabolism pathway may provide an opportunity with great scientific significance and potential value in individualized tumor prevention and clinical treatment.