Objective To develop an Oral Symptom Burden Scale for patients undergoing antitumor therapy and to test its reliability and validity. Methods Based on the theory of unpleasant symptoms, an item pool was constructed based on literature review and semi-structured interviews.A draft of the scale was formed through two rounds of Delphi expert consultation and cognitive interviews.A total of 485 oncology patients were surveyed to test the reliability and validity of the scale. Results The Oral Symptom Burden Scale for patients undergoing antitumor therapy comprises 5 dimensions with 20 items.The average scale content validity index (CVI) was 0.950, and the item-level CVI ranged from 0.857 to 1.000.Exploratory factor analysis identified 5 factors, explaining 76.622% of the total variance.Confirmatory factor analysis showed good fit （χ2/df=2.943,GFI=0.924,CFI=0.952,IFI=0.953,NFI=0.930,TLI=0.944,RMSEA=0.078,SRMR=0.037).The overall Cronbach′s alpha coefficient was 0.913, the split-half reliability was 0.861, and the test-retest reliability was 0.823. Conclusion The Oral Symptom Burden Scale for patients undergoing antitumor therapy demonstrates satisfactory reliability and validity.