Babies do not love to smile may be caused by personality factors, mental retardation, autism and other reasons. 1. Character factor: the baby is relatively young and in good spirits. Not love to smile may be the baby is indeed a character who does not like to smile. It may be due to its own personality. Parents can play games with their babies, smile at them more often, and observe if there are any changes in the babies. 2. Mental retardation: If the baby cannot be made to laugh, and at the same time there are developmental delays, slow response and other abnormalities, attention should be paid to whether there is a problem of intellectual development. 3. Autism: If the baby has no social behavior, such as not responding to being teased and not smiling. If the baby has no social behavior, such as not responding to being teased, not smiling, not making eye contact, not being able to look at others, and not being able to move with the adults to pay attention, attention should be paid to whether the baby is suffering from the possibility of autism. Parents in the exclusion of non-character reasons lead to, should take the baby to the regular hospital in a timely manner, to identify the causes, under the guidance of professional doctors to take targeted treatment.