Population economists argue that different population age structure is related to divergent economic growth rate. Based on existing research on demographic dividend and integrating both quantitative and qualitative methods,this paper examines the effect of demographic dividend on population structure in Zhejiang Province from multiple perspectives,including fertility rate,age structure,dependence ratios,and migration. The author concludes that the demographic window of Zhejiang Province,while emerging early and lasting for a longer period,dissolves rapidly,despite that the inflow of migrants from other provinces has the potential of extending the demographic window. Hence,Zhejiang Province faces double challenges of restricted realization of demographic dividend as well as the demographic debt. Such findings have implications for policy responses to this complex situation.