In the article the author justifies the necessity of studying the formation of the communicative component of language activity of five years old children with GUS through the creation and application of criteria-diagnostic complex on the basis of analysis and synthesis of the psycho-linguistic, psychological and pedagogical, linguistic, speech therapy, teaching literature. Developed criteria and levels of rating will allow to define the levels of formation of cognitive and speech development, which are the basis of communicative component of language activity. On the basis of the received results the content of the method of forming the communicative component of five years old children with GUS can be developed. The key message of the article is the importance of thorough research into the issue of the formation of a communicative component of five-year old children’s speech activity when they have rudimentary speech abilities. In the foreground of the research is speech activity as a functionally complicated bi-directional process; the latter includes the skills, operations and habits being molded in the course of a pre-school children’s development. Special emphasis is made on Ye. Sobotovich’s psycholinguistic model of speech activity and psychological mechanisms underlying its formation. The research provides the analysis of linguistic and communicative components of speech activity, both components being interdependent and closely interrelated. The conclusion is drawn that the disorders of speech activity of the children with general underdevelopment of speaking abilities is caused by rudimentary nature of its structural component, which is manifested in the act of communication. The research contains specific arguments to prove the advisability of pursuing research into a diagnosis of the formation of a communicative component of the speech activity of verbally-challenged children of precisely this age, i.e. 5 year’s olds. The topicality of studying the formation of a communicative component of the children with underdevelopment speech abilities is determined by its importance for an act of communication and transmission of information in the course of oral, mental and intellectual activity as well as the child’s personal maturity.