The least ecological water demand was calculated and the ecological water consumption of different vegetation types was assessed in this paper. The results exhibited that (1) soil moisture and evapotranspiration were closely relative to vegetation types and rainfall. For the same year, soil moisture and evapotranspiration of woodland and shrubland were significantly higher than that of cropland. For the same vegetation types, soil moisture and evapotranspiration in dry year (2002) were lower than that in wet year (2003). (2) Whether wet or dry years, monthly vegetation ecological water using was lower than the least ecological water demand in some months. For yearly scale, the ecological water using of all the six vegetation types in dry year all lower than the least ecological water demand, but higher than the least ecological water demand in wet year (except for wheat). For the averaged rainfall year, ecological water using of potato and H.rhamnoides can reach their least ecological water demand, but the other 4 vegetation types all cannot reach their least ecological water demand. This paper suggested that (1) Arbor and shrub, especially forest, could not be adopted as the major vegetation type. (2) Artificial also can be used to increase the vegetation restoration process.