Abstract: Through reconstruction of the series data on climate and hydrology in Qinghai Lake basin,this paper discussed the effect of climatic change on the water balance for the recent thirty years,from the end of the 1950s to the middle of 1980s. The results indicate that there is a close relation between average precipitation and surface runoff of the drainage. The steady decrease of the Qinghaii Lake level for the recent thirty years is associated with reducing of precipitation,leading to decreasing of the surface supplement to the lake. The models built by the correlation analyses show that the effect of climatic change on the hydrological elements is significant and sensitive. However there are different sensitivit ies for effects of the various climatic elements on the hydrological elements. Precipitation is the most important factor that affects the change of the surface runoff. Air temperature affects not only land evaporation but also the surface runoff. The relation between precipitation and land evaporation is not significant. Therefore,the effect of climatic change on water balance deponds mainly on variations and grouping relation of precipitation and temperature. Suppose that the development of future climate tends to be wet and warm,the change of water balance in Qinghai Lake basin can maintain the present condition,and even the level of the lake rises slightly again possiblly. In addition,the paper also deals with quantitatively the effect of climatic change on underground ice melting in the permafrost region of the drainage basin and the underground ice melting is associated with various hydrological elements. Under the wet and warm situation of future climate, the change of hydrological elements acts totally promoting action on underground ice melting so that it is possible for the lake level to rise.