Pasture lands in Inner Mongolia of China have been deteriorated severely by overgrazing and climate change in the past 30 years. There is a plan to set up a solar irrigation system in Xilamuren area of the region to restore the pastures effectively. In order to design the solar irrigation system based on groundwater, equations for analyzing the optimum irrigation amount were developed in this study, and the main steps to design the system were also given. The coefficients and parameters in the equations are related to meteorological factors, vegetation types and areas, and soil properties. The soil water content is a control variable to decide the water irrigation amount for its effects on maintaining the vegetation growth based on soil water evaporation, plant transpiration and physiological consumption. According to the pasture restoring objectives and water demands during the plants growing periods, proper soil water contents are chosen as evaluation basis for irrigation. The groundwater system should be kept healthy during exploitation; so, the possible supply of local groundwater is a constraint condition in the model. Besides, an optimum irrigation amount process in a whole year is provided for the solar powered system design. (C) 2013 Elsevier Ltd. All rights reserved.