Objective To analyze the effects of different doses of Capecitabine on carcinoembryonic antigen (CEA), carbohydrate antigen 125 (CA125), carbohydrate antigen 724 (CA724) and carbohydrate antigen 199 (CA199) in patients with advanced gastrointestinal tumors, so as to provide reference for clinical treatment. Methods? A total of 62 patients with advanced gastrointestinal tumors who were treated in Suzhou Industrial Park Xinghai Hospital from January 2018 to January 2021 were divided into control group (31 cases, treated with 2 500 mg/m2 Capecitabine) and experimental group (31 cases, treated with 2 000 mg/m2 Capecitabine) by random number table methods, 3 weeks for a course of treatment, patients in both groups were received 3 courses of treatment. Clinical efficacy of patients after treatment, serum CEA, CA125, CA724, CA199 levels before and after treatment, quality of life score, adverse reactions during treatment and 1-year survival rate were compared between the two groups. Results? After treatment, the serum levels of CEA, CA125, CA724 and CA199 in the two groups were significantly lower than those before treatment; the functional assessment of cancer therapy general (FACT-G) scores were significantlyhigher than those before treatment, during the treatment period, the incidences of nausea and vomiting, stomatitis, leukopenia, pigmentation and hand-foot syndrome in the experimental group were significantly lower than those in the control group (all P<0.05); however, after treatment, there were no significant differences in the clinical objective remission rate, levels of serum CEA, CA125, CA724, CA199, scores of social status, emotional status, functional status, physiological status and survival rate at 1-year follow-up between the two groups (all P>0.05). Conclusion? Different doses of Capecitabine in the treatment of advanced gastrointestinal tumors can reduce the level of tumor markers in patients, improve the quality of life, and have definite curative effect; however, compared with the dose of 2 500 mg/m2 , the use of Capecitabine at 2 000 mg/m2 has fewer adverse reactions and higher safety.