The research on the etiology and pathogenesis associated with autism is still unclear. Genetic factors are important factors, especially family lineage and genetic investigations, as well as molecular biology investigations, which show that autism is closely related to genetics, and the heritability is as high as 80%-90%. Immunological studies have found that children with autism have abnormalities in the immune system, especially a low number of lymphocytes and a low number of natural killer cells, all of which to some extent suggest the development of autism. Factors that are unfavorable during maternal pregnancy also have an important influence on the development of autism, especially the advanced maternal age, the father’s advanced age at the time of the mother’s pregnancy or the presence of preterm labor during maternal pregnancy, viral infections, smoking, or the use of certain medications are closely related. Through neurobiochemical studies, autism is associated with 5-hydroxytryptamine levels. About one third of autistic children have increased levels of 5-hydroxytryptamine in their blood, which is not a determining factor but is closely related to autism.