Based on data of relative humidity,precipitation and temperature in the depth 0~20 cm of 19 agricultural weather stations in Liaoning Province from 1981 to 2015,the spatial distribution,long-term changes,the catastrophe features,the periodic characteristics of soil relative humidity were analyzed. The results showed that there was a significant change in soil moisture in the past 35 years. Soil moisture in Liaoxi area decreased (the degree of drought),soil moisture in Liaodong area increased and soil moisture fluctuated yearly.There was no obvious long-term trend and mainly experienced a smooth-partial dry-partial wet three periods. There was no obvious point of change in April and May. There were 4~7 a and quasi-2a cycle respectively.The stability of soil moisture enhanced after 2000. The frequency of soil abnormal dry and extremely wet events increased significantly,especially in the most obvious performance in arid areas of western Liaoning. Soil moisture in April related to autumn precipitation stored in winter frozen soil.Next spring soil melt back to the pulp increased soil moisture. Soil moisture in May related significantly (alpha= 0.01) to the precipitation and temperature in the same period.