Abstract: Water is one of the most sensitive and restrictive factor for the sustainable social and economic development.Especially,in the arid and semi-arid zones,water resources have become one of the pressing critical problem for the economic development and the ecosystem conservancy.Around the proper objective and scale of the ecological environment and the core task of the reasonable utilization of water resources,the paper studies ecological evolution and ecological water demand of Ningxia using the techniques of RS and GIS,and gives some creative suggestions.After the analysis of the ecological significance,the existing ecological conditions and the water resources in the watershed,the theories and studies on the ecological evolution and ecological evolution are put forward with the new ideas of the ecological water demands.