The speech of bilingual children possesses several differences from the speech of monolingual children. The co-existence of two language systems generates many non-standard expressions. Some features of bilingual discourse are peculiar to all bilinguals, other depend on pair of speaker’s languages. The research of Russian-French bilingualism is interesting as linguistic phenomenon. Such research is necessary for further development in linguistics and pedagogics practical methods. The purpose of this paper is to reveal the features of Russian-French children bilingual speech and to analyze the transformations in Russian and French, which are the result of interference between two languages. The paper proposes an approach to the bilingual children speech behavior research. The paper gives an example of analysis of the bilingual child speech language competence consider to different parameters.