This study aims to use structural equation modeling to explore the pathways and effect sizes of factors influencing the adherence of postoperative patients with digestive tract tumor to oral nutritional supplements, providing a theoretical basis for future nursing intervention measures. A total of 300 postoperative patients with digestive tract tumor within 30days after surgery were conveniently sampled. Surveys were conducted using a General Information Questionnaire, Morisky Medication Adherence Scale, Digestive System Tumor Patient Nutrition Knowledge-Attitude-Behavior Questionnaire, Multidimensional Social Perception Scale, Beliefs about Medical Questionnaire, and General Self-Efficacy Scale. Structural equation modeling was employed to analyze the factors and pathways affecting adherence with oral nutritional supplements. The adherence score of postoperative patients with digestive tract tumor to oral nutritional supplements was 1.61 ± 1.38. The structural equation model had a good fit (Ï2/df = 2.685, GFI = 0.930, CFI = 0.913, AGFI = 0.887, IFI = 0.915, and RMSEA = 0.075). Nutrition knowledge, social support, medication beliefs, and self-efficacy were found to be factors influencing adherence with oral nutritional supplements in postoperative patients with digestive tract tumor, with total effects of 0.539, 0.264, 0.215, and 0.180, respectively. Nutrition knowledge indirectly affected adherence through self-efficacy and medication beliefs, while social support indirectly affected adherence through self-efficacy. Adherence with oral nutritional supplements in postoperative patients with digestive tract tumor is at a low level. Improving social support, enhancing patients nutrition knowledge, increasing self-efficacy, and strengthening medication beliefs are effective ways to improve patient adherence.