Abstract: Using temperature and precipitation data of 248 stations in Northwest China,from interannual change,interseasonal variability and durability characteristic posted regional drought and wetness evolvement over Northwest China in recent half century by homogenized drought-wetness index of precipitation and evaporation. The result showed that drought-wetness evolvement characteristic exist clear difference between driven by temperature and precipitation and driven by precipitation,this illuminated that contribution of climate warming to drought trend of Northwest China is marked. Since 1990 anaphase probability of abnormal drought month showed increase trend in every subarea,but that of abnormal wetness month lean to fewness in recent 10 years except for North Xinjiang,and the phenomenon is especially stand out for southeast of Northwest China. From season view,winter could hardly occur abnormal drought phenomenon in mostly area of Northwest of China,but it showed drouthy trend in spring,summer and autumn,in additional since 1990 durative wetness event had hardly occurred in southeast of Northwest China,east of Qinghai tableland and south of Xinjiang,and durative drought event much more than that of before 1990s,and maximal duration was long,intensity was also strong,frequency,intensity and duration of north of Xinjiang have not clear trend change in recent 48 a,in despite of frequency of durative drought than that of durative wetness in Qinghai tableland,but it was fewer than that of other area’s,and intensity was waeker,duration was short.

Key words: the Tibetan Plateauu, summer half year, winter half year, heavy rainfall days, temporal and spatial distribution