Objective To develop and validate a self-management rating scale for gastrointestinal cancer patients undergoing chemotherapy (SMRS-GCC). Methods Based on the COSMIN checklist, draft of the SMRS-GCC was formulated using literature review, interview of gastrointestinal cancer patients and expert consultation. Then 211 patients were surveyed to provide data for item analysis and exploratory factor analysis (EFA). At last, 361 patients were surveyed to test the reliability and validity. Results Six factors of 24 items were identified through EFA, accounting for 75.361% of the total variance. The factors were labeled physical symptom management, drug related management, nutritional management, medical cooperation and information acquisition, emotional management and role management. Confirmatory factor analysis indicated the model fit well (χ2/df=2.442, CFI=0.935, and RMSEA=0.063). The Cronbach′s alpha coefficient was 0.930 for the total scale, and test-retest reliability was 0.979 for the total scale. Conclusion The SMRS-GCC is reliable and valid to measure self-management ability of gastrointestinal cancer patients during chemotherapy.