Objective To explore the effects of multimodal nursing intervention on constipation, difficulty in defecation, quality of life, trait anxiety, and nursing satisfaction in patients with gastrointestinal tumors undergoing radiotherapy and chemotherapy, and to provide a basis for optimizing clinical nursing models. Methods A randomized controlled study design was adopted, in which 80 patients with gastrointestinal tumors undergoing radiotherapy and chemotherapy admitted to Sun Yat-sen University Cancer Center were randomly divided into an observation group and a control group, with 40 cases in each group. The control group received routine nursing, while the observation group received multimodal nursing interventions on the basis of routine nursing, including personalized dietary guidance, exercise intervention, psychological support, and biofeedback training. The incidence of constipation, difficulty in defecation score, quality of life score, trait anxiety score, and nursing satisfaction score before and after intervention were observed. The data was analyzed using SPSS 26.0 for statistical analysis. Results After intervention, the incidence of constipation in the observation group was significantly lower than that in the control group (15.00% vs 45.00%, P<0.001), with an improvement rate of 62.50%; The observation group showed a significant decrease in defecation difficulty score after intervention [(1.75± 0.56) points vs (3.12±0.68) points, P<0.001]. In terms of quality of life scores, the observation group showed significant improvements in physical, psychological, and social dimensions compared to the control group (P <0.001). The observation group showed a significant decrease in trait anxiety scores after intervention, with scores in all dimensions significantly better than the control group (P<0.001). The nursing satisfaction score showed that the overall satisfaction of the observation group was higher than that of the control group [(4.71±0.49) points vs (3.85±0.72) points, P<0.001]. The improvement in communication and response dimensions was particularly significant. Conclusion Multimodal nursing intervention significantly alleviates constipation and difficulty in defecation in patients with gastrointestinal tumors undergoing radiotherapy and chemotherapy, improves their quality of life, reduces trait anxiety, and increases nursing satisfaction. This nursing model provides a scientific basis for optimizing the comprehensive nursing practice of patients with gestrointestinal tumors and has broad clinical promotion value.