Abstract: To explore the changes of the four seasons in Inner Mongolia under the background of global warming, and provide a scientific basis for the adjustment of local agriculture-animal husbandry industry and the protection of ecological environment, the monitoring data of 101 meteorological stations in Inner Mongolia from 1961 to 2016 were used as materials, and the variation of the beginning date and length of the four seasons were analyzed with the method of Seasonal Division of Climate (QX/T 152-2012). The results showed that the spatial distribution of the beginning dates of spring, summer and autumn in Inner Mongolia delayed gradually from southwest to northeast, but the beginning date of winter was just the opposite. The length of spring was longer in the middle and shorter in both ends in Inner Mongolia. The length of summer and autumn reduced from southwest to northeast, and there was no summer in central region of Hulun Buir, and the distribution in winter length was opposite to that in summer and autumn. According to the interannual change, the beginning dates of spring, summer and autumn were all in advance, and the seasonal length also showed an increasing trend. But the beginning date of winter was delayed, and the length of winter was shortened. Under the background of global warming, the beginning date and length of the four seasons in Inner Mongolia changed obviously, and had a certain effect on agriculture-animal husbandry production and ecological average.