Abstract: In order to study the soil desiccation and yield fluctuation of high yield maize on Loess Plateau,the EPIC model was used to simulate water potential productivity(WPP)of spring maize and soil water dynamics on rain-fed highland at Changwu County of the Loess Plateau for a medium term (12 years) assessment and a long term(30 years)forecast simulated research,respectively.The results show that during 12-year real-time weather condition simulation period,WPP of spring maize on rain-fed highland fluctuates and declines along with precipitation changes,crop available soil water amount in 3m soil layer also fluctuates and declines evidently,and the trend of soil desiccation is remarkable.During 30-year simulated weather condition simulation period,WPP of spring maize on rain-fed highland fluctuates along with precipitation but declines slightly;crop available soil water amount in 3m soil layer fluctuates seasonally and annually,and has a light increase trend for a long term period.Soil desiccation of maize field on rain-fed highland is a short time phenomenon and usually does not last for long time if the declining trend of precipitation is not distinct,but the fluctuation of maize yield along with precipitation change is inevitable.