Climate models are important tools to study the effects of climate system and climate change,climate model results is important basis for weather forecast and climate change risk assessment. The northwest arid area of China is sensitive to climate change,and is one of the regions where atmosphere and land is strongly coupled. However, the current climate models still remain a lot of uncertainties about the region's simulation results. Therefore,it is necessary to access simulated results of climate models,which could provide scientific basis for climate modes' improvement and simulation ability. Based on the observed average temperature and precipitation of seventy-eight weather stations from 1960 to 2005 in the study area,the simulation ability of annual average temperature and precipitation from the latest thirty-nine CMIP5 modes were evaluated,adopting the indices such as correlation coefficient, mean absolute error,root-mean-square error and interannual variation. The results indicated that the correlation coefficients between simulated and observed data reached to 0.39,and the correlations in summer and autumn were better than those in spring and winter,the simulated annual average temperatures were 2 ℃ less in the most cases,mean absolute error of annual average temperature simulated by MIROC4h,CCSM4 and CMCC-CM is lower. The correlation coefficients between simulated and observed precipitation on the yearly and seasonal scales were very poor and less than 0.1,and the precipitation was overestimated by 100 mm in the most cases, mean absolute error of annual precipitation simulated by CMCC-CM,CNRM CM5 and MRI-CGCM3 is lower. As for the interannual variation trend,the rising trends of simulated annual average temperature and simulated precipitation were lower than that of observation,the rising trend of simulated average temperature in winter reached to -0.21 ℃/10 a and was the lowest. The rising trend of simulated precipitation in summer was the lowest and the mean error was close to -99%. On the whole,there are the marked differences between simulated values and observed values,especially for simulated precipitation. Simulation ability of climate modes in the northwest arid area of China is in need of further improving, physical mechanism of climate system is worth doing a study in depth,and the modes should be modified reasonably.