Objective To investigate the effect of nutritional intervention compliance on nutritional status and clinical outcome of patients with malignant tumor with severe malnutrition. Method A retrospective analysis was performed on 506 patients with malignant tumor and severe malnutrition admitted to the Department of Oncology from April 2019 to June 2021. The patients were screened and evaluated by nutritional risk screening NRS 2002 tumor nutrition assessment PG-SGA and simple dietary self-assessment tools. Using nutritional treatment principle of five steps to nutrition diagnosis treatment and curative effect evaluation and follow - up nutrition therapy plan according to the patient􀆳s compliance to group 2 weeks after treatment with nutrition to assess patients compliance score < 6 points into poor compliance group scoring six points into the good compliance group or higher Blood routine albumin prealbumin physical fitness height weight and other nutritional indicators were monitored in 2 groups. Result After nutritional intervention for tumor patients under 60 years old for two weeks the changes of blood potassium albumin grip strength and weight loss rate in two weeks were better in patients with good compliance than those with poor compliance all P < 0. 05 . The changes of RBC albumin prealbumin CRP grip strength and twoweek weight loss rate in tumor patients aged 60 years and over after nutritional intervention for two weeks were better in patients with good compliance than in patients with poor compliance all P < 0. 05 . The physical status score of tumor patients with good compliance 2 2 3 was lower than that of tumor patients with poor compliance 3 2 3 and the dietary score 3 1 3 was higher than that of tumor patients with poor compliance 2 1 3 . Patients with PS score < 3 points or ≥ 3 points and dietary score < 3 points or ≥ 3 points had better compliance than those with poor compliance in terms of albumin prealbumin grip strength and weight loss rate within two weeks after nutritional intervention all P < 0. 05 . Conclusion After standardized nutritional therapy patients with malignant tumors with severe malnutrition showed significant improvement in rapid changes such as albumin and prealbumin moderate changes such as grip strength and weight loss rate after 2 weeks in patients with good compliance.