Abstract: OBJECTIVE To investigate the relationship of TCM constitution classification with infection during chemotherapy, immune function and gastrointestinal flora in patients with gastric cancer chemotherapy. METHODS A total of 180 patients who underwent chemotherapy for gastric cancer in Hanchuan People's Hospital from Jan. 2018 to Jan. 2021 were selected as the study subjects. TCM constitution typing was performed based on the symptoms and clinical manifestations of the patients. The incidence of infection during chemotherapy, immune function indicators, distribution of gastrointestinal flora, toxic and side effects of chemotherapy and prognosis were compared among gastric cancer patients with different types of TCM constitution. RESULTS Of the enrolled 180 patients with gastric cancer chemotherapy, 42 cases developed infection during chemotherapy, with an infection rate of 23.33%. There were 31 cases of liver-stomach disharmony type, 31 cases of deficiency-cold in spleen and stomach type, 33 cases of qi stagnation and blood stasis type, 12 cases of phlegm-dampness coagulation type, 60 cases of qi-blood deficiency type, and 13 cases of stomach heat injuring yin type. There were statistically significant differences in the infection rate, T-lymphocyte subpopulation (CD₄⁺ and CD₃⁺) and natural killer cells (NK) during chemotherapy in patients with different types of TCM constitution (P<0.05). A total of 61 pathogenic bacteria were detected in the gastric fluid specimens of 42 patients with chemotherapy infection, of which 23 strains of Gram-positive bacteria accounted for 37.70%, 36 strains of Gram-negative bacteria accounted for 59.02%, and 2 strains of fungi accounted for 3.28%, and the detection rate of gastrointestinal flora in patients with deficiency of Qi and blood was significantly higher than that of other types (P<0.05). The incidence of toxic and side effects after chemotherapy in patients with disharmony of spleen and stomach, deficiency of cold of spleen and stomach and deficiency of Qi and blood was significantly higher than that in other types of TCM constitution (P<0.05). After 3-6 months of follow-up after chemotherapy, it was found that the overall survival rate of gastric cancer patients with Qi and blood deficiency was significantly lower than that of other types of TCM constitution (P<0.05). CONCLUSION Patients with gastric cancer had a bi-frequency constitution after chemotherapy, with qi deficiency, phlegm dampness and yang deficiency constitution symptoms predominating. Patients with peaceful and qi deficiency constitution were more prone to toxic and side effects after chemotherapy, and the TCM constitution symptoms had a certain influence on the prognosis of patients.