Abstract: Based on the meteorological observation data of 107 weather stations in Inner Mongolia, mean monthly temperatures, mean monthly air humidity and annual rainfall distribution of kilometer-scale are calculated using gradient method of inverse distance square law. Taking the raster data into Ivanov moisture degree calculation formula, the moisture degree of kilometer-scale in Inner Mongolia Autonomous Region are obtained. Combined with the distribution regularity of actual vegetation types of Inner Mongolia, climate zoning index of grassland types in Inner Mongolia are identified. Five grassland types are defined in Inner Mongolia as meadow steppe, typical steppe, desert steppe, steppe desert, and desert. With the grassland type climate zoning index, partition boundaries of grass yield are determined. On the basis of output distribution in each partition, six grass yield levels of climate zoning index are obtained, which are grass yield greater than or equal to 2000, 1600—2000, 1100—1600, 900—1100, 800—900 kg·hm^-2, and less than 800 kg·hm^-2, respectively. And then humidity raster data could be classified by using these climate zoning indexes. After that, the zoning map of grassland type in Inner Mongolia Autonomous Region natural grassland could be drawn. In addition to that, the zoning map of geographical distribution of grass yield could also be got. Afterwards data of 65 field investigations samples as well as 49 ecological observation sites are used in a reliability test, for climate zoning results. The reliability analysis shows that division results and the distribution of actual grassland types in Inner Mongolia have good consistency, indicating that the grassland climate zoning can better reflect the spatial distribution regularity of natural grassland types. Hence, the grassland type division results can be used for climatic regionalization in Inner Mongolia grassland. Due to neglecting the soil texture, economic and other non climate factors, there is a certain error on the boundaries between the sand, grass crisscross midwest and different grassland type areas. For each district, its geographical position, climate characteristics and grassland utilization status are reviewed, and furthermore, related analysis, countermeasures and suggestions on rational distributions are given. In conclusion, the results can provide a scientific basis for adjusting agricultural structure and optimizing livestock layout in Inner Mongolia Autonomous Region.