A child who is four years old and still can’t speak may be due to hearing impairment, mental retardation, autism and other reasons. 1. Hearing impairment: the child can not hear the external sound signals, so the child can not speak at the age of four. 2. Mental retardation: brain damage, delayed central nervous system development, resulting in mental retardation caused by four-year-old still can not speak, usually accompanied by open mouth and tongue, low bridge of the nose, wide orbits and other symptoms. 3. Autism: in addition to not being able to speak, autistic children usually can not interact with their partners to play, their behavior is relatively dull, and they like to play alone. If a child is four years old and still can’t speak, it is recommended to take the child to the hospital for examination, to clarify the cause of the disease and to treat it as soon as possible.