Objective To observe the efficacy of all trans retinoic acid (ATRA) combined with 5-Fu on treating subcutaneously implanted gastric carcinoma SGC 7901 in the nude mice. Methods Thirty-two nude mice bearing tumor were randomly divided into 4 groups: control group (group A), ATRA 1 000 μg/d orally taken group (group B), 5-Fu 27 mg/kg group peritoneally injected (group C), 5-Fu 13.5 mg/kg combined with ATRA 500 μg/d group (group D). Results Significant inhibition of tumor growth was shown in the group B, group C and group D as compared with group A (Ｐ＜0.01), with the tumor growth inhibition rate and the tumor weight inhibition rate at the 7 weeks after the treatment being 56.88%, 49.00%, 70.00% and 56.10%, 51.64%, 76.95%. Conclusion ATRA combined with 5-Fu can enhance the effects of 5-Fu in treating gastric carcinoma.