Soil moisture droughts can trigger abnormal changes of material and energy cycles in the soil-vegetation-atmosphere system,leading to important effects on local ecosystem,weather,and climate.Drought detection and understanding benefit disaster alleviation,as well as weather and climate predictions based on the understanding the land-atmosphere interactions.We thus simulated soil moisture using land surface model CLM3.5 driven with observed climate in China,and corrected wet bias in soil moisture simulations via introducing soil porosity parameter into soil water parameterization scheme.Then we defined soil moisture drought to quantify spatiotemporal variability of droughts.Over the period from 1951 to 2008,40%of months(to the sum of 12×58)underwent droughts,with the average area of 54.6%of total land area of Mainland China.The annual monthly drought numbers presented a significant decrease in arid regions,but a significant increase in semi-arid and semi-humid regions,a decrease in humid regions but not significant.The Mainland as a whole experienced an increasing drought trend,with77.3%of areal ratio of decrease to increase.The monthly droughts in winter were the strongest but the weakest in summer,impacting 54.3%and 8.4%total area of the Mainland,respectively.The drought lasting three months or more occurred mainly in the semi-arid and semi-humid regions,with probability>51.7%,even>77.6%,whereas those lasting 6 and 12 months or more impacted mainly across arid and semi-arid regions. Soil moisture droughts can trigger abnormal changes of material and energy cycles in the soil-vegetation-atmosphere system, leading to important effects on local ecosystem, weather, and climate. Drought detection and understanding benefit disaster alleviation, as well as weather and climate predictions based on the understanding the land-atmosphere interactions. We thus simulated soil moisture using land surface model CLM3.5 driven with observed climate in China, and corrected wet bias in soil moisture simulations via introducing soil porosity parameter into soil water parameterization scheme. Over the droughts, with the average area of ​​54.6% of total land area of ​​Mainland China. annual monthly drought numbers presented a significant decrease in arid regions, but a significant increase in semi-arid and semi-humid regions, a decrease in hum id regions but not significant. Mainland as a whole experienced an increasing drought trend, with 77.3% of areal ratio of decrease to increase. monthly monthly in winter were the strongest but the weakest in summer, impacting 54.3% and 8.4% total area of ​​the Mainland, respectively. the drought lasting three months or more occurred mainly in the semi-arid and semi-humid regions, with probability> 51.7%, even> 77.6%, while those lasting 6 and 12 months or more impacted mainly across arid and semi-arid regions.