The Autism Mental Status exam (AMSE) has demonstrated excellent sensitivity and specificity in Western high-risk population with suspected autism spectrum disorder (ASD). This study aimed to evaluate the psychometric properties of the AMSE in a sample of high-risk Chinese children, and to determine the optimal cutoff score of the Chinese version of the AMSE in supporting ASD diagnosis. 66 young children aged from 2 to 11 years with suspected ASD were enrolled in the present study. A diagnosis of ASD or non-ASD was determined by a Best Estimate Diagnosis protocol according to the DSM-5 criteria. Receiver operating characteristic (ROC) curve analysis was conducted to assess the validity of the AMSE and search for the most effective cutoff score. The ROC curve analysis yields the area under the ROC curve of 0.98 which represents excellent diagnostic accuracy. Findings indicate the optimal cutoff score of the Chinese version of the AMSE was estimated as 6, producing the highest sensitivity of 98% and a specificity of 87%. Preliminary findings of the study suggest the AMSE has promising psychometric properties as an assessment tool for identifying ASD symptoms and supporting diagnostic decision-making in high-risk Chinese children population.