Abstract: Based on data of field water experiments on typical steppe of Inner Mongolia in 2008, a crop coefficient of the typical steppe was calculated from analysis of the water amount balance, and changing regularity during the growing season. Simulation equations of the crop coefficient built with number of days after grass revival in a year and accumulated temperature above 0℃, showed that simulation using a cubic polynomial expression was appropriate and correlation coefficients were all over 0.94. Typical values of crop coefficients were defined with a linear section method of FAO, and they were 0.43 in the initial growing period, 1.02 in the medium growing period and 0.90 in the final stage. A method of revising the crop coefficient of typical steppe under stress conditions was put forward with leaf area index (LAI). The crop coefficient given in this article was suitable for typical steppe in Inner Mongolia, because simulating calculation of soil water was mostly close to the results of actual observations with mean relative simulation errors of 6.2%-13.6%.