Abstract: Synapse is an essential component in function and information transmission between neurons, hence the role its dysfunction played in the pathology of autism has received much attention. The synaptic morphology changes have been found in animal model or patients of autism, mainly manifested by abnormalities in dendritic spine density, proportion of the dendritic spines and postsynaptic density(PSD), which are possibly correlated with interruptions in formation, maturation and maintenance of synapses. In addition, deletions and point mutations of the synaptic proteins such as NRXNs, SHANK3, NLGNs genes have been detected in ASD individuals. Multiple signaling pathways have been reported to affect the social contact ability in ASD models, possibly caused by synapse function disruptions. Until now, the pathogenesis and drug targets of autism still remains unknown, and thus pose great challenges to further studies. This review focuses on the role of synaptic dysfunction in human ASD.