Abstract: Based on the Chinese census data of 1990, 2000 and 2010, this paper has analyzed the fertility of the second birth, TFR and progression fertility, used the 1% sample of 2005 and 2010 census data to set up the population simulation model. Using the simulation model, this paper has estimated the total population of only-child is 145 million in 2010 and only-child-death population is 1.08 million since the family planning policy conducted in China. If the current family planning policy keeps going in the future, the total only-child population will reach 300 million and the only-child-death population will increase to 11.84 million in 2050. And the new only-child-death family will increase from 95 thousand in 2010 to 560 thousand for each year in 2050. For the population size of only-child-death family increasing, government and society should pay more attention on them.