Understanding the meaning of words makes it possible to understand the picture of the world. Language is a person's ability to communicate facts, objects and actions through words. Linking the same concept with the corresponding word, i.e., determining the meaning of the word, is possible thanks to semantic processing. An important issue in cognitive science is the study of how the meanings of words are represented and classified in the human cognitive system. And the most important sign of children with autism in society is a speech disorder. The vast majority of them have varying degrees of language impairment. The lexical and semantic aspects of speech are particularly important. Semantics is the study of the content of a word that comes to consciousness and is pronounced. The lexical and semantic side of the speech of children with autism depends on the severity of the autism and the cognitive abilities of the child. For this reason, it is important to diagnose the lexico-semantics of a child with autism in the work of correction and integration into the environment. One of such diagnostic methods is the method of N.V. Serebryakov, L.S. Solomokhov, which determines the volume and quality of passive and active vocabulary. And the article describes an attempt to analyze the effectiveness of this technique using the experience of scientific research.