Abstract: A large weighing lysimeter and micro-lysimeters were used to measure the process of evapotranspiration and soil evaporation during four growing seasons of summer maize under different irrigation shedules. The results showed that the change of total evapotranspiration was large among years, among which the change of total transpiration is larger, the range of transpiration changes from 158.44 mm to 233.99 mm; The soil evaporation　changing is small, the range of soil evaporation changes from 171.43 mm to 181.52 mm. The ratio of soil evaporation to the evapotranspiration changes from 43.57% to 52.52%. The effects of rain, irrigate and weather condition on the soil evaporation of summer maize in growth period are insignificant, but their effects on the transpiration are significant. Under sufficientand unsufficient irrigation condition, the related coefficients between the ratio of E to ET and LAI are above 0.85 and 0.77.