Abstract: Urbanization comes along with population increment and centralization,which enlarges the density of impervious areas,results in dwindling ground water replenishment and deteriorating urban water cycle etc.In order to have a better understanding and quantify the impacts from reducing impervious areas and installing rainwater catchment systems on long-term urban water cycle,building up an appropriate urban water cycle model is needed.The watershed of the Liu-guan pumping system in Taipei city has been chosen as the study area.Parameters in the rmdel are calibrated and verified using measured data from the inflow of the pumping station.Sensitivity analysis of these parameters is also conducted.The hydrologic changes among surface runoff,infiltration and evapomanspiration for changing percentage of impervious areas by installing permeable pavement are examined.Also different percentages of existing buildings are assumed to install roof rainwater catchment systems and their impacts on surface runoff and water supply are evaluated.The urban water cycle model established in the study may easily assess the changes of water cycle by changing land uses and provide as a useful tool for urban planners.