The spatial characteristics and yearly,seasonally and daily variation properties of total cloud cover is analyzed in this paper based on every-three-hour mean monthly data of ISCCP from July,1983 to December,1993 over the Tibetan Plateau which is divided into 39 grids.Some scientific explanation are also made for the moisture condition,topographic dynamics and circulation patterns over the Plateau.Comparing the distribution of total cloud cover from ISCCP with that observed from surface stations,the rationality of ISCCP-D2 data is validated.It is concluded that there is a good(poor) correlation in summer(winter) by analyzing the correlation between the total cloud cover and OLR.