As an important forcing factor of the land surface,permafrost is very sensitive indicator of climate change. The freeze-thaw process is directly involved in local energy and water cycles,and in turn affects weather and climate. In this study,using the multi-model results from the fifth phase of the Coupled Model Intercomparison Project(CMIP5),we computed the near-surface permafrost area on the Qinghai-Xizang Plateau(QXP)via surface frost index(SFI)method,and assessed the ability of models to simulate the related climate variables and present-day(1986 -2005)permafrost,by comparing with the reanalysis products and the frozen soil map of the QXP. Based on this assessment,the climate models were aggregated by arithmetic mean to project the changes of permafrost on the QXP under the four different Representative Concentration Pathways(RCPs). The results show that the CMIP5 coupled models have some simulation capabilities for permafrost on the QXP. The simulated present-day near surface permafrost distribution is similar to the plateau frozen soil map,with the annual average of permafrost area of 127.5*10~4 km~2(1986 -2005). The prediction results by multi-model ensemble mean indicate that the permafrost appear a degradation tendency on the QXP,especially on the eastern,southern and the edges of northern plateau. The permafrost will shrink from the edges to the north-west inner part of the QXP, and most probably exist only in the northwestern regions by 2099. Using the SFI method,the rate of the permafrost area change under RCP2.6,RCP4.5,RCP6.0 and RCP8.5 scenarios are -2.2*10~4 km~2·(10a)-1,-5.9* 10~4 km~2·(10a)-1,-5.4*10~4 km~2·(10a)-1 and -10.0*10~4 km~2·(10a)-1,respectively. In the next 50 years,the permafrost area will decrease about 23.9*10~4 km~2(20.8%),33.5*10~4 km~2(27.7%),25.6*10~4 km~2(21.1%) and 43.5*10~4 km~2(35.3%)under RCP2.6,RCP4.5,RCP6.0 and RCP8.5,respectively. The average values of permafrost area in the last period of 21st century are about 91.4*10~4 km~2(RCP2.6),70.9*10~4 km~2(RCP4.5),72.8*10~4 km~2(RCP6.0)and 41.7*10~4 km~2(RCP8.5). Although there are large ranges in degree of degradation for different scenarios,the linearity of relationship exist between the permafrost area and the surface air temperature.