Abstract: Using data from 2015 China Family Happiness Survey, the standardized family happiness score is calculated, a comparative analysis is made between parents of only-child families and the ones of other families. The findings are as follows. Firstly, the fulfillment of fertility desire plays a very important role in family happiness. Secondly, parents of only-child have significantly higher family happiness than other parents. Thirdly, parents who born in 1980s and 1970s have higher family happiness. It is suggested that the universal two-child policy decreases the gap between people's fertility desire and fertility policy, which will improve people's family happiness, social harmony and population long-term balanced development.