In the context of the universal two-child policy, this paper investigates the impact of grandparent care and formal childcare on fertility desire of secondchild based on the national fertility survey conducted in 2017. Using binary logistic regression and propensity score matching methods, we find that both of the two childcare modes have significant effects on the fertility desire of secondchild but their influencing directions are opposite: the grandparent care significantly increases the propensity to have the second child, while the formal childcare has a negative impact. Further study shows that the number of kindergartens per capita in prefecturelevel cities plays a positive moderating effect, weakening the role of formal childcare in reducing the fertility desire, while the average childcare costs in prefecturelevel cities play a negative moderating effect, strengthening the negative effect of formal childcare on fertility desire of the second child. Therefore, this paper suggests that increasing the supply of affordable public childcare services is the most effective policy to increase the fertility desire to have a second child.