Abstract: Objective: To develop a knowledge assessment questionnaire for childhood developmental disorders, to test its reliability and validity, and to explore its application value among caregivers of children with developmental disorders. Methods: Based on expert consensus and relevant guidelines, two rounds of expert consultation and a pre-test were conducted to form the questionnaire. Stratified sampling was employed to select six children's rehabilitation institutions across regions with varying levels of economic development in Hunan Province as the study sites, and a total of 252 primary caregivers of children with developmental disorders were recruited for the investigation. The knowledge assessment questionnaire and medical-seeking behavior questionnaire were used to collect data for further testing the reliability and validity of the developed questionnaire. By using the median grouping method, the caregivers were divided into a high-knowledge group and a low-knowledge group. The differences in medical treatment and rehabilitation behaviors were compared between the two groups, and the reference cut-off value of the questionnaire was determined accordingly. Results: The finally developed knowledge questionnaire consisted of 4 dimensions and 18 items. The item-level content validity index (I-CVI) ranged from 0.93 to 1.00, and the scale-level content validity index (S-CVI) was 0.98. Confirmatory factor analysis results revealed that the model fitted well comparative fitted index (CFI)=0.898, root mean square error of approximation (RMSEA)=0.069. The overall Cronbach's α coefficient of the questionnaire was 0.798, and both McDonald's ω coefficients and Cronbach's α coefficient of each dimension were all greater than 0.7. Based on the median total scores of the questionnaire (15 points), caregivers in the low-knowledge group (scores≤15 points) were more likely to experience delayed diagnosis and treatment, and showed poorer compliance with rehabilitation treatment. Therefore, it was suggested that 15 points be taken as the reference cut-off value of the questionnaire. Caregivers with scores≤15 points were considered to have inadequate knowledge and require targeted health education. Conclusion: The knowledge assessment questionnaire for childhood developmental disorders has good reliability, validity and discrimination ability. It can be applied to scientific research and clinical health education practice related to the diagnosis, treatment, and rehabilitation of childhood developmental disorders.