Objective·To explore the influencing factors of oral nutritional supplement compliance in postoperative patients with digestive tract cancer based on COM-B model,and to analyze the mediating role of medication belief and self-efficacy in oral nutritional supplement.Methods·A total of 300 postoperative gastrointestinal cancer patients were selected by convenience sampling method.The General Information Questionnaire,Morisky Medication Adherence Scale,Digestive Cancer Patients Nutrition Knowledge,Attitude and Practice Questionnaire,Multidimensional Scale of Perceived Social Support,Beliefs about Medicines Questionnaire and General Self-Efficacy Scale were used.A mediating effect model was used to analyze the influencing factors of compliance with oral nutritional supplements.Results·The score of Morisky Medication Adherence scale was 1.61±1.38,which was at a low level.Oral nutritional supplement compliance was significantly positively correlated with nutrition knowledge,social support,medication belief and self-efficacy(r=0.391,0.401,0.438,0.410,all P＜0.01).Medication belief had a partial mediating effect between nutrition knowledge and adherence to oral nutritional supplements(effect size=0.097,accounting for 18.00%of the total effect).Self-efficacy had a partial mediating effect between nutrition knowledge and oral nutritional supplement compliance(effect size=0.044,accounting for 8.16%of the total effect).Self-efficacy had a partial mediating effect between social support and oral nutritional supplement compliance(effect size=0.044,accounting for 16.67%of the total effect).Conclusion·The compliance of oral nutritional supplements in postoperative patients with gastrointestinal cancer is at a low level.The individualized nursing intervention can increase the nutritional knowledge of patients,improve the social support,reduce the concerns of patients about oral nutrition,and improve the self-efficacy of patients,so as to promote the compliance of patients with oral nutritional supplements.