Abstract： Objective： To observe the efficacy of Shenyu Yangwei Decoction combined with oxaliplatin， leucovorin，and 5-fluorouracil（FOLFOX4）chemotherapy regimen in treating middle-advanced stage gastric cancer. Methods：A total of 120 patients with middle-advanced stage gastric cancer treated at the First Affiliated Hospital of Nanyang Medical College from June 2022 to June 2024 were selected and divided into a control group and an observation group，with 60 cases in each group，using a random number table method. The control group received FOLFOX4 chemotherapy，while the observation group additionally took Shenyu Yangwei Decoction on the basis of the control group. After eight weeks of treatment，the traditional Chinese medicine syndrome scores and immune function index level were compared between the two groups before and after treatment. Clinical efficacy was assessed， and the classification of chemotherapy-related toxic and adverse reactions during treatment was recorded. Results： The objective response rate in the observation group was 61.67%（37/60）and the disease control rate was 90.00%（54/60）， compared to 35.00%（21/60）and 75.00%（45/60）in the control group，respectively，with significant differences between the two groups（P＜0.05）. After treatment，the traditional Chinese medicine syndrome scores in both groups were decreased compared to before treatment（P＜0.05），with the observation group achieving lower scores than the control group（P＜0.05）. The levels of CD3 + ，CD4 + ，and CD4 + /CD8 + in both groups were decreased compared to before treatment（P＜0.05），with the observation group achieving higher levels than the control group（P＜0.05）. During treatment，the observation group had lower grades of toxic and adverse reactions such as nausea，vomiting，leukopenia and thrombocytopenia compared to the control group（P＜0.05）. Conclusion：Shenyu Yangwei Decoction combined with the FOLFOX4 regimen can improve clinical efficacy and the traditional Chinese medicine syndromes in treating middle-advanced stage gastric cancer， reduce the impact of chemotherapy on immune function， and alleviate chemotherapy-related toxic and adverse reactions.