This　paper　provides　a　methodology　of　calculating　urban　surface　runoff　based　on　GIS.　The　content　mainly　includes:　delineating　flow　path　on　basin;　determining　concentration　time;　drawing　isochrones;　generating　effective　rainfall　hyetograph;　calculating　surface　runoff,　The　methodology　is　demonstrated　by　using　data　for　the　west　campus　of　Beijing　TECH.　Compared　with　the　traditional　manual　method,　the　method　of　urban　surface　runoff　calculation　based　on　GIS　is　more　feasible　and　more　efficient,　and　shows　great　promise　in　the　future.　The　methodology　may　be　transferable　to　other　regions　where　GIS　data　is　available.