Autism is seen as social development disorder caused by brain developmentdisorder when fetus grows abnormally, or at the first year of life. Generally, thesymptoms can be seen since the children is under 3 years old. Most of parents are late todiagnose the abnormality of children. It's caused by high cost of consultation and theyhave to queue.Naïve Bayes Method is the method for this expert system. The methods willdiagnose the children with autism and classify the autism categories to be low autism,medium autism, or high autism. There are 33 autism symptoms that the systems willprocess it. After being tested, the expert systems can diagnose children with autism thesame as the expert's (psychologist) diagnose.