Background There may be differences in gender and marital status in the impact of grandchild care on the depression of the Chinese older adults. This research explores the effect of grandchild care on the depression of Chinese older adults of different genders and marital status, and explores the mediating role of intergenerational support from children between grandchild care and depression. Methods This research uses the data of 3540 Chinese older adults from the China Health and Retirement Longitudinal Study (CHARLS) in 2018. The OLS model is used to analyze the effect of grandchild care on the depression of the older adults. and the older adults are classified according to gender and marital status, and the differences in the effect of grandchild care on the depression of the elderly of different genders and marital status is explored. Finally, the bootstrap method is used to test the mediating effect of intergenerational support from children. Results The research finds that grandchild care has a significant impact on the depression of the older adults in China, and providing grandchild care can significantly reduce the depression of the older adults. The effect of grandchild care on the depression of the older adults is different between different genders and marital status. After categorizing the older adults by gender, the grandchild care only has a significant impact on the depression of female older adults; after classified by marital status, grandchild care only has a significant impact on the depression of the older adults who don’t have a spouse. The mediating effect analysis shows that both children’s emotional support and children’s economic support have a mediating effect between grandchild care and depression of the older adults. Conclusion The depression of the Chinese older adults is affected by grandchild care, and this effect is more prominent in female older adults and the older adults who don’t have a spouse. The society should support and encourage capable older adults to participate in gr...