Rainfall interception is an important hydrological process occurred in soil-plant-atmosphere continunm(SPAC). Understanding the hydrological response in vegetation will help us improve water use efficiency. In this paper, an investigation of leaf water absorption and desorption was conducted through two land cover plants of white clover (Trifolium repens L.) and milk vetch (Astragalus adsurgens Pall.) under simulating rainfall conditions. The purpose was to evaluate the capacity of water retention in the leaf level. The results showed that the leaf water absorption of the two plants was rapid at the initial stage of rainfall interception, tended to be slowness after one hour, and finally got a threshold, which is turgid leaf water content. While the intercepted water by leaf faded away, the leaf started to get desorption. The processes of leaf water desorption of the two plants were similar to the process of leaf water absorption. The rate of desorption was rapidly at the initial stage after water on the leaf surface faded away, then tended to be slow down while a time, and finally got a threshold of leaf water content. Relative to the process of water absorption, the process of water desorption lasted longer time. The models of both water absorption and desorption can be expressed as: C=C0(1-e-kt). The results also showed that turgid leaf water content rose linearly with the increase of SLA.