By using Caterpillar-SSA analysis method, through the process of embedding, singular value decomposition, grouping and diagonal averaging, the seasonal precipitation trend at north Helan Mountain and Baiyinaobo regions, Inner Mongolia for the next 20 years is forecasted. The results show an increasing precipitation trend from 1992 to 2004. In the subsequent decade the precipitation should reduce quickly, and it will reach a minimum near 2012 to 2014 in both regions. The drought caused by the decrease of the precipitation from May to July in the north Helan Mountain area during the period of 2013-2014 is probably quite similar to that around 1929. Further, the period of precipitation gradual increase follows in the researched regions.