Abstract: Based on the lowest daily temperature and the earliest frost occurrence date of 119 meteorological stations in Inner Mongolia Autonomous Region from 1981 to 2010, the maturity date of the 80% guarantee rate of different climate ecoregions was used as the boundary date to assess whether the soybean [Glycine max （Linn.） Merr.] frost disaster occurred. The climate hazard risk index system of frost disasters was constructed to analyze the evolution characteristics of Inner Mongolia soybean autumn frost and spatial distribution characteristics. The results showed that in the 30a time scale, different grade autumn frost of soybean occured in Inner Mongolia were slightly smaller trend, but the early frost days of different grades showed an early trend. The regional characteristics of frost occurrence were obvious, and the range of light frost occured in relatively large areas, and the interannual variation of light frost was obvious, and the date of occurrence was also significantly in advanced. The distribution law was that the frequency of autumn frost in different grades was generally high in the northeast, was low in west and southeast. The coefficient of variation and the spatial distribution of intensity and frequency were relatively consistent, and the regions with large variability were mainly distributed in the Daxinganling mountains and Yinshan mountains. Through the construction of climate hazard risk index model and classification of risk climate index, there was a large spatial difference for the risk of autumn frost in Inner Mongolia, the area with high risk of frost was concentrated in the northeast region. And among them, the south of Daxinganling was agricultural area that was one of the major soybean producing areas of Inner Mongolia. There is an advantageous condition for ensuring a high harvest of soybeans that mastering the change law of frost, rationally arranging crop varieties and familiarity, doing a good job in disaster prevention and mitigation and meteorological services for agriculture in the region.

Key words: soybean[Glycine max （Linn.） Merr.], autumn frost, interannual variation, dangerous, climate hazard risk index, Inner Mongolia Autonomous Region