Abstract: Against the background of unlimited two-child policy, fertility behaviors in families show positive externalities in social security, since fertility gets irrelevant with pension as a result of pension from social security and personal savings. In order to release fertility, it is imperative to correlate pension with family fertility to return to the form of caring for the elderly by children in family, or impose social alimony for the old age on Dink, low birthrate and single families, and take the alimony to subsidize families with more children. In the time span between 2015 and 2030, baby-boomers in the 1960s will start to retire. Since caring for the elderly in an aging society will occupy fertility resources, it is necessary to put off the retirement age for people born in the 1960s, so as to postpone the tide of retirement and pension and release fertility, for the sake of generating demographic dividends. To further avoid further occupancy of fertility resources by pension system in an aging society, it raises the suggestion that it should be better to offer pension products than offering pension. Through establishing nursing homes, it will transform the traditional care for the elderly in a dispersed way to collective support, to reduce the cost of caring for the elderly and realize the purpose of releasing fertility. In the end, in the premise of no cut on pension resources, no lowering the children's quality and no decrease in output, young people should strive to create a social culture of abstinence.

Key words: fertility2.0 era, public good, DINK Family fertility behavior tax, delay retirement, geracomium