Abstract: The establishment and reform of China's population policy is accompanied by the process of demographic transition, which has created favorable conditions for the rapid development of social economy after the reform and opening up. This paper reviews the population policy and demographic transition since the founding of new China. The family planning policy underwent germination, criticism and stagnation; it was restored after the Cultural Revolution; since the reform and opening up, the family planning policy was further established and stabilized, it was fine-tuned and adjusted to the population situation since 2000. The demographic transition is mainly manifested in two aspects of birth and death. The fertility level has declined rapidly and stabilized at a low level, the reproductive age is delayed continuously, and the reproductive pattern has changed significantly; the life expectancy of the population is prolonged, the infant mortality rate and the maternal mortality rate are significantly reduced, the pattern of death cause and death structure are changing to the old-age type, and the national health has been at the forefront of the developing countries. However, the post-demographic transition era is a test of China's economic and social development system, and we need to be prepared.