In recent years， there has been a shift in the approach to using grey infrastructure for rainwater and flood management， and the rainwater and flood regulation and storage function from the perspective of blue-green synergy has begun to be emphasized. To explore the reduction effect of various green space regulation methods on rainfall runoff， taking the South Lake catchment zone of Wuhan City as the research object， this paper simulates the changes in the total annual runoff control rate， peak flow and peak time under the sponge green space renovation measures based on the SWMM （storm water management model）， revealing the effect of green space on reducing rainwater runoff in the urban catchment zone from the perspective of blue-green synergy. The results show that： the transformation of concave green space with a scale of 20%-30% for urban catchment zones can achieve the sponge city construction goal of an annual runoff control rate of 65%.Among different sponge green space transformation measures， there is no significant difference in the effect of complex concave-down green space （with aquifer and lower pipe） and simple concave-down green space （without aquifer and lower pipe） on a single rainfall event. However， the performance of complex concave green space will be more significant for long-term and multi rainfall situations.