Objective To explore the effects of immunonutrition on tumor-infiltrating T-lymphocytes and regulatory T-cells in rectal tumor patients receiving neoadjuvant chemoradiotherapy. Method Prospective selected 120 rectal tumor patients admitted to the Oncology Department of Liyuan Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology from September 2020 to June 2023 divided into 2 groups according to the random number table method. The control group of 60 patients were treated with routine nutritional support in the observation group 60 patients received immunonutritional support cancer cell proliferation and apoptosis PI AI AI / PI gastrointestinal hormone levels VIP MTL GAS tumor infiltration and regulatory T lymphocyte numbers Th3 TGF-β CD3 + CD8 + and nutritional status PA Hb ALB at 30d after treatment. Result Cancer cell proliferation and apoptosis gastrointestinal hormone levels nutritional status tumor infiltration and regulated T lymphocytes were better than before treatment P <0. 05 . Comparison of the post-treatment effects between the two groups observation group PI AI AI / PI VIP MTL GAS Th3 TGF-β CD3 + CD8 + . the improvement was better than that in the control group The difference was statistically significant P<0. 05 . Meanwhile the treated PA Hb ALB were higher than the control group with statistically significant differences P<0. 05 . Conclusion Immunonutritional support for rectal tumor patients receiving neoadjuvant radiotherapy and chemotherapy can promote cancer cell apoptosis inhibit cancer cell differentiation and proliferation improve nutritional status and gastrointestinal function and improve body immunity which is the preferred treatment mode for rectal tumor.