Autism spectrum disorder（ ASD） is a group of severe and highly heterogeneous neurodevelopmental disorders， which is the result of a combination of genetic factors and complex environmental factors. The pathologic mechanisms are still unclear. A large number of studies suggest that epigenetic mechanisms， especially abnormal miRNA expression in specific brain regions， may be involved in the occurrence and development of ASD， and circulating miRNA is expected to be a biological marker for early diagnosis.