Two very important demographic events occurred in May 2021．One is that the National Bureau of Statistics released the major figures of the seventh population census．The other is that the political bureau of the CPC Central Committee held a meeting to further optimize the family planning，which allows couples to have three children and supporting measures．The 2020 census recorded a lowest fertility rate in Chinese history，with the total fertility rate being only 1.3．Population ageing becomes faster，and there are drastic transformations in the population of China．As a policy response，the birth policy has been significantly adjusted，from a universal two－child policy to a three－child policy．Estimation using the census data suggests that China ’s total fertility rate stood at1.5—1.8 over the past decade．A demographic decomposition analysis demonstrates that marriage postponement has been depressing fertility，and the two-child policy has had a marked impact on lifting up the second child fertility．Fading away of the effects of the two-child policy leads to a more rapid decline in fertility．The implementation of the three-child policy provides space for the pursuit and realization of the moderate fertility rate，the adjustment of regional population development and the satisfaction of the diverse fertility needs of different groups．
