Autism is a physical and mental condition that cause significant social, communication, and behavioral challenges. There is often nothing about how people with Autism Spectrum Disorder (ASD) look that sets them apart from other people. Still, people with ASD may communicate, interact, behave, and learn in ways that are different from most other people. The learning, thinking, and problem-solving abilities of people with ASD can range from gifted to severely challenged. Early diagnostic of ASD is very essential because delay detection may cause an increase in severity level. Autism diagnostic tools can play a significant role in the early detection of ASD. There are several diagnostics tools for ASD detection. The main objective of this study was to evaluate autism diagnostic tools among the children and find out the diagnostic outcome of early detection of ASD by systematic review. Some authentic databases like PUBMED, Google Scholar, Scopus were searched using keywords of relevant topics, and a protocol was developed with defined inclusion and exclusion criteria.