In most cases, it is not normal for a 21-month-old baby to be unable to speak. If we define speech as “expressing meaning and opinion in words”, usually 21-month-old babies are able to use simple words and sentences. If a 21-month-old baby is unable to pronounce words at all, he or she should be alerted to abnormal speech development due to environmental and disease factors. Parents need to take their children to the pediatric department of a regular hospital for relevant examinations in order to make a clear diagnosis. Parents should communicate with their children, create a good language environment, and expose their children to language activities and TV programs to promote the brain thinking ability and language expression ability. And patiently guide and actively encourage the child to vocalize, may accelerate the progress of the child’s speech learning; Second, pathological factors are common in vocal cord hypoplasia, hearing impairment, autism, etc.. It is necessary to seek timely medical attention and treat the disease symptomatically under the guidance of professional doctors. Parents also need to accompany their children more in daily life and give them confidence in treating the disease. 1. congenital vocal cord dysplasia: articulation habits should be corrected early; 2. neurological damage: long-term, regular language rehabilitation training is required; 3. autism: professional psychologist’s help can be sought for speech learning and behavioral training; 4 Hearing impairment: auditory training or hearing aids can be provided. Note if the child’s language environment is poor, such as parents do not communicate with the child, mixed language environment, etc., can also affect the child’s vocalization. So parents need to interact more with their children and try to unify the language communication to promote the child’s vocalization.