Aging is a major trend of global population development. In order to release fertility potential and slow down the aging process of the population, China will implement the “three-child” policy from 2021. Taking the policy object as the starting point, grounded theory is innovatively used to interview 40 interviewees with purposeful sampling, and the reasons for the cold implementation of the “three-child” policy and the corresponding implementation path from the bottom up are explored. It is found that the execution of cold is essentially an adverse selection under the compound effect of internal pressure and external pressure in the reproductive population. The internal causes are the shift from “quantity” to “quality” in the target group's conception of fertility, the high risk of female fertility and the lack of family parenting support. The external triggers are high economic pressure, heavy workplace pressure, and insufficient medical education for childbirth. Accordingly, it is suggested to guide the transformation of childbirth, improve the fertility environment and strengthen policy guarantees.The fertility support system will be built to improve the implementation effect of the “three-child” policy.