In 2002, "Extreme Male Brain Theory of Autism" was proposed by Professor Baron-Cohen at the University of Cambridge. In his theory, autism is thought to be an extreme form of the typical male cognitive style. The female mentality, characterized by empathy, is usually deficient in autism, while male mentality, characterized by systematism, is greatly developed. This theory was established on the basis of the empathizing-systemizing theory, and then developed into the hyper-sensitizing theory. Although facing some challenges, the theory has gained support in many disciplines: psychological, neurological, biological, etc. In particular, a high intrauterine testosterone level was found in the fetus with autism, as demonstrated by digit ratio, handedness, play behavior, parental occupation, as well as islets of ability, etc. This theory provides us with a new perspective for understanding autism.