This study examined the association between the grandparenting and mental health, and the mediating role of family cohesion.The Center for Epidemiological Studies-Depression Scale(CES-D), Satisfaction with Life Scale(SWLS), and Family Cohesion subscale of Family Environment Scale(FES) were used to assess depressive symptoms, life satisfaction and family cohesion,respectively. A self-developed questionnaire with a single item measured frequency of grandparents’ caring for grandchildren. Data were collected through a community survey. A total of 325 community-dwelling grandparents(aged ≥ 45) years were investigated.The results showed that caregiving frequency was negatively associated with both depressive symptoms and life satisfaction, which indicated that the grandparenting had both positive and negative effects on grandparents’ mental health. Moreover, family cohesion partially mediated the relationship between caregiving frequency and depressive symptoms, and the relationship between caregiving frequency and life satisfaction. In conclusion, the grandparenting had both positive and negative roles in mental health of middle aged and elderly people as grandparents, and family cohesion partially mediated the above relationship.