As a most developed region in China Taihu Basin which with a quickly economic development has a important status in China economic development.The economic characters of Taihu Basin are quick development,large urbanization and economic difference in spatial distribution.Impacts to floods by some pyromania of eco-society development,such as land use change urbanization economic development polder construction were analyzed in this paper.The main conclusions included: (1) economic development made flood losses increase; (2)as land use changed, runoff increased; (3) land surface sedimentation resulted flood control engineering lost some capacities;(4) polders protect some land from flooding, but polder construction led quicker runoff.