Objective The aim of this study is to estimate the prevalence of autism spectrum disorder(ASD) among 18-36 month old children in the Tianjin Municipality of China, and to identify early signs of autistic children and the predictability of each individual symptom. Methods A total of 8 000 children were screened to do a questionnaire based on CHAT modified to include more early signs of autism at the age of 18-36 months. Then the at-risk children were reexamined 1.5 years later and ASD children were identified based on DSM-IV. Early signs of autism were analyzed retrospectively by using discriminant function analysis performed among ASD children, children not followed up and children followed up but failing to meet ASD criteria. Results Three hundred and sixty seven children were screened as being at-risk to ASD, and 22 of them were identified as having ASD in the subsequent diagnosis. The prevalence of ASD was 27.5 per 10 000 in Tianjin of China with a male to female ratio of 4:1. Items addressing social interactions and communications had higher predictability than other items to distinguish autistic children from non-autistic ones. Pretend play, functional play, showing and reading parents’ facial expressions distinguished autistic children from those not followed up, nevertheless those followed up but failing to meet ASD criteria were not included. Conclusion The prevalence of ASD found in our study was lower than that reported in some studies by western researchers. Autism has its specific symptoms, such as deficits in social awareness, social relatedness, and social referencing. Objective The aim of this study is to estimate the prevalence of autism spectrum disorder (ASD) among 18-36 month old children in the Tianjin Municipality of China, and to identify early signs of autistic children and the predictability of each individual symptom. Methods A total of 8 000 children were screened to do a questionnaire based on CHAT modified to include more early signs of autism at the age of 18-36 months. Then the at-risk children were reexamined 1.5 years later and ASD children were identified based on DSM Early signs of autism were analyzed retrospectively by using discriminant function analysis performed among ASD children, children not followed up and children followed up but failing to meet ASD criteria. Results Three hundred and sixty seven children were screened as being at-risk to ASD, and 22 of them were identified as having ASD in the subsequent diagnosis. The prevalence of ASD was 27.5 per 10,000 in Tianjin of China with a male to female ratio of 4: 1. Items addressing social interactions and communications had higher predictability than other items to distinguish autistic children from non-autistic ones. Pretend play, functional play, showing and reading parents’ facial expressions distinguished autistic children from those not following up, nevertheless it followed up but failing to Meet The prevalence of ASD found in our study was lower than that reported in some studies by western researchers. Autism has its specific symptoms, such as deficits in social awareness, social relatedness, and social referencing.