This paper based on GIS land suitable assessment principle and method, use supermap to analysis suitability of crop land of liao city. The suitability of comprehensive analysis was conducted in Study area for three crops .First, choosing representative and having the same impact the suitability of natural factors and social economic factors of the three kinds of crops; Then, interpolation and empowerment of overlap and analysis in supermap, and the appropriate level of land were classified according to land on crops. Thus can adjust measures to local conditions to crops layout and farming system reform and adjustment, the biggest production potential play land. Experimental results show that in the complex crop suitability assessment process, GIS is an effective, possible means.