Two and a half years old will only call mom and dad may be the baby lack of language exercise, but also may be the intellectual development delay or autism and other reasons. 1. Lack of language exercise: If you rarely communicate with your baby on language, and your baby has less time to speak, your baby will lack language communication, which will lead to delayed language development, this situation should be more and more language communication with your baby, but also let your baby have more contact with other children, it will help language development. 2. Mental retardation: some babies have mental retardation, their language development will be relatively backward, and their gross motor development and social skills will also be backward compared to children of the same age. 3. autism: the child is two and a half years old will only call mom and dad and there may be autism. The two and a half years old will only call mom and dad to pay attention to, it is recommended to actively go to the regular hospital for relevant examination, clear diagnosis, follow the doctor’s instructions to adopt the appropriate solution.