Autism spectrum disorders (ASDs) are a complex neurodevelopmental disorder that display restricted interests, repetitive behavior, impairments in language and communication, and an inability to engage in social interactions. The causes of the ASDs remain unknown for the majority of individuals with ASD. ASD is among the most heritable disorders. Family studies indicate that up to 25% of cases can be identified as a genetic cause. Chromosomal rearrangements as well as rare and de novo copy-number variants (CNVs) are present in ∼10–20% of individuals with ASD, compared with 1–2% in the general population and/or unaffected siblings. Evidences show the single-nucleotide polymorphisms (SNPs) seem to contribute to ASD susceptibility. These findings, coupled with genome sequencing data may unveil the genes implicated in ASDs. This paper summarizes the results of molecular genetic research on autism and mainly introduces the genetic risk factors such as CNVs, SNPs and candidate genes for autism spectrum disorders to provide relevant information.