The system of evaluating losses of flood disaster is one of important components of flood-proof decision-making system in Taihu Lake catchment and it can accurately forecast and evaluate the flood disaster in Taihu Lake catchment at the same time provide scientific foundation to flood-proof.This paper from GIS application & developmental point of view introduces the technique systems of GIS software, the frame of technology, the characteristic and effect of spatial database as well as main functions of the system.