Three and a half years old still can not speak, may be related to language development delay, may also be due to hearing problems, autism and other reasons. 1. Delayed language development: it is mostly considered that it may be related to the baby’s growing environment. If the baby has less contact with the outside world since childhood, and the family relationship is not coordinated, the parents have less communication with the child, and the child is in such a closed environment for a long time, it may result in the child’s delayed language development. 2. Hearing problems: If a three-and-a-half-year-old baby has a hearing impairment, due to the inability to hear the outside world, it may lead to their own inability to learn to speak, resulting in three-and-a-half years old and still can not speak. 3. Autism: three and a half year old babies who suffer from autism can also cause different degrees of language development disorders, resulting in the phenomenon of not speaking, may also be accompanied by stereotyped behavior, poor language comprehension and other symptoms. Three and a half years old still can not speak, but also for other reasons, it is recommended to consult a doctor as soon as possible, after diagnosis of the cause, give targeted treatment.