Autism spectrum disorder (ASD) is counted as a worldwide public health problem. The possible causes of ASD are reactive oxygen species and free radicals. So, this study is aimed to evaluate the effects of Gallic acid, as an effective antioxidant, on histopathologic disorder of the cerebellum in valproic acid-induced autism animal models. 30 pregnant female rats were randomly divided into 5 groups, including: control, autism (or VAP) and experimental 1, 2 and 3. Using a gavage needle, Gallic acid administered orally until about2 months of age. After the end of the treatment period, the rats were anesthetized with ether and their cerebellar tissues were removed for histopathologic studies. A significant decrease in the number of Purkinje and granular cells was observed in this study in VAP group compared to the control group (P≤0.05). A trend toward improvement was observed in the groups received 100 and 200 mg/kg of Gallic acid (P≤0.05). The results of this research revealed that Gallic acid reduces the side effects caused by valproic acid on cerebellar tissue of autistic rats. So, it should be considered for therapeutic goals.