Autism is a representation, a general characterized by "a bunch of failure" to describe and categorize individuals behavior describing failures in social relationships, communication, and imagination ability. To develop ability on children with autism to be close to normal, diagnosis methods through early, integrated and intensive treatment were used. One type of therapy for children with autism is through food or the so-called Gluten Free Casein Free (GFCF) diet therapy. The type of this research was descriptive with cross sectional design. The population in the study were all students with autism who were still active following treatment with a sample of 36 people who were taken by using purposive sampling. Results showed that mostly there are 80.6% parents who have knowledge, 55.6% samples never eat foods containing gluten, 50% samples never eat foods containing casein, 77.8% samples have a good energy intake, 100% samples have good protein intake, and 80.6% samples have mild autistic behavior. From the results of the study, it is expected that the parents can increase knowledge about the GFCF diet in order to improve their diet and reduce behavior disorders in autism children