ObjectiveTo systematically review the relationship between cadmium (Cd) and childhood autism.MethodsPubMed, EMbase, Web of Science, The Cochrane Library, CNKI, VIP, WanFang Data and CBM were electronically searched to collect case-control studies on the relationship between Cd and childhood autism from inception to July 2019. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies. Then, meta-analysis was performed by using RevMan 5.3 software.ResultsA total of 8 case-control studies were included. The results of meta-analysis showed that whether the specimen was from whole blood, urine or hair, there were no correlations between Cd and childhood autism (MDblood=0.17, 95% CI ?0.06 to 0.39, P=0.15; MDurine=?0.43, 95%CI ?1.44 to 0.58, P=0.4; MDhair=?0.08, 95%CI ?0.52 to 0.36, P=0.72).ConclusionsCurrent evidence shows that Cd concentration is not correlated with autism in children. Due to limited quality and quantity of the included studies, more high quality studies are required to verify above conclusions.