Objective:To develop the Postoperative Subdelirium Syndrome Knowledge, Attitude, and Practice Questionnaire for Surgical Nurses and test its reliability and validity.Methods:Based on the theory of knowledge, attitude, and practice, the preliminary Postoperative Subdelirium Syndrome Knowledge, Attitude, and Practice Questionnaire for Surgical Nurses was developed through literature search and analysis, Delphi expert consultation, and pre-survey. From February to April 2022, convenience sampling was used to select 375 surgical nurses from five Class Ⅲ Grade A hospitals and three Class Ⅲ Grade B hospitals in Zhejiang Province for questionnaire item analysis, exploratory factor analysis, and reliability testing.Results:The final Postoperative Subdelirium Syndrome Knowledge, Attitude, and Practice Questionnaire for Surgical Nurses consisted of 33 items in three dimensions of knowledge, attitude, and practice. Exploratory factor analysis extracted three common factors with a cumulative variance contribution rate of 67.016%. The total Cronbach's α coefficient of the questionnaire was 0.931, and the Cronbach's α coefficients for each dimension were 0.972, 0.906, and 0.932, respectively. The overall test-retest reliability coefficient of the questionnaire was 0.999, and the test-retest reliability coefficients for each dimension were 0.997, 0.994, and 0.998. The questionnaire-level content validity index was 0.889, and the item-level content validity index was 0.833 to 1.000.Conclusions:The Postoperative Subdelirium Syndrome Knowledge, Attitude, and Practice Questionnaire for Surgical Nurses has good reliability and validity, and can be used to evaluate the knowledge, attitude, and practice of postoperative subdelirium syndrome among surgical nurses.