The article examines the theoretical foundations of preventing written speech disorders in children with severe speech impairments. The concept of speech in speech therapy is revealed, the relationship between oral and written speech is analyzed, and the necessity of forming prerequisites for written speech at preschool age is substantiated. Special attention is paid to children with severe speech impairments as a risk group for dysgraphia and dyslexia. The main areas of speech therapy work are identified: development of phonemic perception, sound analysis and synthesis, lexical and grammatical structure of speech, coherent speech, visual-spatial representations and graphomotor skills.