Objective To observe the curative effects and adverse reactions of synchronous tegafur chemotherapy combined with three-dimensional conformal radiotherapy on colorectal cancer. Methods From Mar. 2014 to Mar. 2016, 60 patients with colorectal cancer were collected in our hospital, which were randomly divided into observation group and control group with 30 cases in each group. Both groups were given three-dimensional conformal radiotherapy, besides, the observation group was given additional synchronous tegafur chemotherapy. The short-term and longterm effects, and adverse reaction of chemotherapy in the two groups were observed and compared. Results All the patients completed treatment, and 1 month after treatment, the total effective rate in the observation group was 80.0% which was significantly higher than that in the control group 50.0% (P<0.05), the median disease-free progression time in the observation group was 11.3 months which was significantly higher than that in the control group 8.5 months (P<0.05), the main adverse reactions in the two groups were nausea and vomiting, neutropenia, anemia, bone marrow depression and radioactive enteritis, and these symptoms were all I-II degrees, but there was no significant difference in the incidence of adverse reactions between the two groups (P>0.05). Conclusion Synchronous tegafur chemotherapy combined with three-dimensional conformal radiotherapy which has good curative effect in the treatment of colorectal cancer, can significantly prolong the survival time of patients. Its toxic and side effects are all below Ⅲ degree, therefore, it is tolerable for patients.