Background: Autism is the most common clinical developmental disorder in children. The Childhood Autism Rating Scale (CARS) and Autistic Behavior Checklist (ABC) are the most commonly used assessment scales for diagnosing autism. The aim of this study is to compare the diagnostic validities of CARS and ABC based on a large Chinese sample.Methods: A receiver operating characteristic (ROC) curve was used to compare the diagnostic validities of CARS and ABC, as well as the corresponding cut-off determinations was calculated.Results: A total of 474 children with suspected autism spectrum disorder (ASD) were screened by CARS and ABC. Receiver operating characteristic (ROC) curve analysis was performed and it showed that the area-under-the-curve values of CARS is higher than ABC significantly (p <0.05) and the suggested cutoff values of CARS and ABC were 34 and 67, respectively.Conclusion: This study demonstrated that CARS was superior to ABC in terms of its diagnostic validity of assessing suspected ASD cases in children. Based on our results, we recommend the CARS could be used for the assessments for suspected ASD cases in Chinses hospitals.