In the past two or three decades, China’s fertility rate has been below the replacement level and declining. The problem of low fertility rate is likely to affect economic vitality, national competitiveness, and the operation of social security system, and even threaten national security. In view of this, the Decision on Optimizing the Fertility Policy to Promote the Long-term Balanced Development of Population puts forward to “further optimize the fertility policy and implement the policy of one couple having three children and supporting measures”. Therefore, the decline in fertility and the policy to support fertility have attracted great attention from all walks of life. The rising cost of parenting is considered to be an important factor for the decline in fertility, and the key of the cost lies in the work-childrearing conflicts caused by caring for children in families. In view of this, how to alleviate the conflicts, reduce the cost of parenting, and improve fertility has increasingly become a common concern of the whole society. The 14th Five-Year Plan for National Economic and Social Development of the People’s Republic of China and the Outline of Long-term Goals for 2035 clearly states: “Reduce the burden of fertility, parenting and education, release the potential of fertility, develop inclusive childcare service system, and strictly implement the policy of supporting kindergartens in urban communities. ”The reason why kindergarten supply reduces the cost of raising is that it can alleviate the conflicts and liberate families from all-day care for children. With the employment of the quasi-natural experiment of the policy of “establishing kindergartens by social forces” in 2003, this paper matches CHIP2013 data with the number of kindergartens based on prefecture-level cities, and uses the cross-sectional DID method and instrumental variable methods to find that the policy has a positive impact on the number of children in families. On average, an increase of 0.1 units in intensity of the policy will lead to an increase of 0.012 children in affected families. This means that in the five years since the implementation of the policy, if there are 20 million families affected by the policy every year, the average number of children in families will increase by an additional 1.2 million. The reason behind it is that the expansion of kindergarten supply will help families save time for caring for children, alleviate the conflicts, and then improve fertility. Further, the fertility effect of the policy is heterogeneous among families. For families with higher conflicts, such as families with higher education, families with more distant between family members, or families with long working hours, the positive fertility effect of the policy is greater. Moreover, the positive impact of this policy on fertility is relatively higher in areas with larger road pavement. This may be because better road paving conditions can compress the time and space distance, improve the accessibility of kindergartens, and then reduce the conflicts to a large extend.On the one hand, this paper makes up for the relative deficiency of domestic literature on the fertility effect of the expansion of kindergarten supply; on the other hand, kindergarten education and childcare services for children aged 0-3 have the same function in terms of alleviating the conflicts. In fact, this paper also provides empirical evidence for China to develop inclusive childcare service system to improve fertility. The policy suggestions are that: Firstly, increase the supply of kindergartens to ensure the nearby admission. Secondly, reduce the time and space distance between families and kindergartens, effectively shorten the time cost of approaching and using kindergarten services, and improve the accessibility of kindergartens.