The current paper considers peculiarities of mothers' speech behavior in interaction with preschool children with Down syndrome (DS). Perceptual, phonetic, instrumental spectrographic analysis of mothers' speech and analysis of non¬verbal behavior in 20 dyads “mother – child with DS” at the age of 4–7 years were carried out. Particular patterns of the interaction of mothers with children with DS are revealed, the strategies for speech interaction correlated with a high and low level of speech development in a child are identified. Mother¬to child speech analysis showed that mothers make long phrase¬final pauses, their speech is emotional, they repeat a question or similar words while interacting with the child, address the child by the name. Firstly, it was found that mother’s repetition of questions or similar words pronounced by the child is connected with the certain level of speaking skills developed in the child, particularly, clear articulation and the use of words and phrases in their responses. Another discovery was that the mother’s use of simple grammar and marking certain words with the voice correlated with the low level of the child’s speaking skills when the speech is unclear and the child just repeats the mother’s words. Although, the mother’s behavior is centered around the child’s speaking and cognitive abilities, it does not always result in the progress in child’s speech development, however, it is critical for this development. The data obtained may be useful to parents and caregivers of children with DS.