An effective assessment of regional rainfall-induced landslide potential using the GIS-based deterministic model is presented. This study adopts the Transient Rainfall Infiltration and Grid-based Slope-stability model (TRIGRS, developed by USGS) which couples an infinite-slope stability analysis with a one-dimensional analytical solution for rainfall infiltration to evaluate the regional landslide potential. Simultaneously, the rainfall threshold for each sub-watershed could also be obtained. The Typhoon Morakot event was taken as an example. The initiation locations of landslides for several dangerous villages and important transportation junctions in the mountain area of Kao-Ping River watershed are successfully predicted by the model and the spatial overlapping technique of GIS. The preliminary results can be regarded as good references for the scheming an early warning system in the future.