The period when environmental impact can play the greatest role in the process of individual development. In the critical period, under the influence of suitable environment, behavior acquisition is particularly easy and develops rapidly. However, if there is no suitable environmental impact at this time, it can also cause pathological reactions and even hinder the normal development in the future. In the critical period, the body is extremely sensitive to the environmental impact and can also respond to micro-stimuli. Some researchers renamed it sensitive period. The researchers also found that at the beginning and end of the critical period, the body's sensitivity to the environment is low, and it is the highest in the middle period. But if there is no certain influence, it will cause developmental variation. The study of critical period has aroused strong repercussions in educational practice. First, it publicizes the importance of early childhood education. Recent studies have proved that children have great potential in childhood, and the critical period of children's development is mostly in infancy. Therefore, the implementation of early education can give full play to children's learning potential, promote children's psychological development, and help to train talents at an early stage. Secondly, urge parents and teachers to choose the best time to educate their children, so that children can easily master knowledge and skills and easily form intelligence and personality. Therefore, corresponding to the critical period of children's development, the best period of education work is put forward. The introduction of the concept of critical period should be pushed to the study of Austrian anthropologist K.Z. Lorenz. Lorenz found that both chickens and goslings were born with marks. He pointed out that individual imprinting can only occur in a short "critical period" in an individual's life, and the object imprinted by the individual at this moment can make the individual close to it and have a preference, and will not be forgotten, thus forming a permanent bondage attachment to it. Lorenz's research has attracted psychologists' attention to the critical period, and a lot of research has been done. The most important thing is to explore and put forward the critical period of children's development in all aspects. For example, some researchers have found that the most vulnerable critical period of human embryos is within 6 weeks after pregnancy, that is, the development period of major organs. All congenital defects occur in the first three months of pregnancy. Some researchers have suggested that the critical period of brain development is from the fifth month after birth to the 10 month. In the meantime, if we neglect or lack good environmental education, our development will be damaged. In addition, it also puts forward a critical period for children's language and psychological development. Psychology also studies the influence of the development of individual critical period on future development. Many studies show that children from birth to 3 or 4 years old, if deprived of perceptual experience, lack of social communication, neglect of intellectual education or care for their parents, will seriously affect their normal psychological development in the future. The critical period needs further study, and it should be noted that: ① The critical period of children's development should be scientifically determined and cannot be simply inferred. ② Make full use of the good opportunities in the critical period and take active educational measures to promote development, instead of waiting for natural development. ③ Pay attention to the role of critical period in development, but not limited to this; Children or adults who miss the critical period can still achieve good development through proper education.