In accordance with the characteristics of many geographical objects and many complex influencing factors existing in dam-break loss evaluation, an evaluation method of loss caused by dam-break based on GIS and support vector machine is put forward. Calculation methods and influencing factors of loss caused by dam-break are analyzed. The evaluation index system is established by the grey relation degree model. The method and implementation process on the evaluation of loss caused by dambreak according to the combination of GIS and SVM model are discussed in detail. Application shows that the evaluation method have good effect and high precision.