Objective To develop a nursing intervention program for improving adherence to oral nutritional supplementation post-operatively in patients with gastrointestinal tumors. Methods Based on the Behavior Change Wheel,the draft of a nursing intervention program was developed through literature review and semi-structured interview.Then 2 rounds of expert consultation were conducted with 19 experts through the Delphi method. Results The return rate of questionnaires was 100% in both rounds, and the authority coefficient of the expert was 0.910. The mean score of importance for each item ranged from 4.11 to 5.00 points. The nursing intervention program included three primary indicators, six secondary indicators, and twenty-four tertiary indicators. Conclusion This nursing intervention program developed based on the Behavior Change Wheel for improving adherence to oral nutritional supplementation in postoperative gastrointestinal tumor patients is scientific and comprehensive, which may play a positive role in this population.