Objective To develop a Knowledge, Attitude, and Practice (KAP) Questionnaire on Home Modification for Aging in Place Among Community-Dwelling Older Adults, and to provide a basis for implementing targeted interventions. Methods Based on the Knowledge, Attitude/Belief, and Practice (KAP) theory, a questionnaire on home modification for aging in place among community-dwelling older adults was developed through literature review, group discussions, and Delphi expert consultations. Convenience sampling was used to select 541 elderly residents from four communities in Harbin and Qingdao for the questionnaire survey, followed by item analysis and reliability and validity testing of questionnaire. Results The Knowledge, Attitude, and Practice (KAP) Questionnaire on Home Modification for Aging in Place Among Community-Dwelling Older Adults included 44 items across three dimensions: knowledge, beliefs, and behaviors. The cumulative variance contribution rate of the exploratory factor analysis was 64.635%; the confirmatory factor analysis showed that the model was fit well (χ2/df=2.568, RMSEA=0.076, GFI, AGFI, RFI, NFI, CFI, IFI, TLI all >0.900); the content validity index at the scale level was 0.886, and the content validity index at the item level was 0.882~1.000; the overall Cronbach′s α coefficient of the questionnaire was 0.949, and the retest reliability was 0.766. Conclusion The Knowledge, Attitude, and Practice (KAP) Questionnaire on Home Modification for Aging in Place Among Community-Dwelling Older Adults has good reliability and validity and can serve as an assessment tool for evaluating the KAP level of home geriatric modifications among community-dwelling older adults in China.