By using the ArcViewGIS Citygreen 5.0 model,six different land cover categories in the second ring road of Xi'an City were digitized,data of precipitation and soil hydrologic characters were analyzed,and benefits from storm-runoff reduction by urban forest were quantified.It was found that the total benefit from storm-runoff reduction was 150 682.06 m3 for the typical 24 h storm events of 3.2 cm in summer.Landuse categories,in terms of the net discharge reduction,were in the descendant order of residential area,road,park,culture area,industrial area,and commercial area.The storm-runoff reduction benefit per hectare was mainly related to impervious surface and forest coverage,and landuse categories were in the descendant order of park,road,culture area,industrial area,residential area,and commercial area.