Abstract: Groundwater in a many regions is an important support or supplement for ecological stability,the critical depth of recharge of surface vegetation by groundwater is critical to groundwater management and ecological security. Taking the West Liaohe Plain as an example,five results were concluded as follows:① The moisture movement structure in vadose zone was innovatively demarcated based on recharge of the vegetation by groundwater,and the mechanism and physical process of recharge of the vegetation by groundwater were described,and the critical depth of recharge of the vegetation by groundwater and related physical concepts were defined. ② According to the physical mechanism of absorbing the phreatic evaporation by the root system of the vegetation,the phreatic water affected layer which is formed by the rise of the capillary water is the key to critical depth. ③ The rational formula of the soil effective pore size was deduced,and the porosity parameter was calculated based on crystal structure model of soil particles,which dissolved the precise calculation of the maximum height of capillary water. ④ The calculation model for critical depth of recharge of the vegetation by groundwater was built by thickness of the root system. ⑤ The results were confirmed by massive field surveys. The results of the study were timely applied in the Horqin Grassland.