A kind of K drought index and its criterion are made by using spring precipitation and evaporation data of 140 stations in Northwest China from 1971-2000.At the same time,the comparison is done among the defined K drought index,improved Palmer drought index and precipitation anomaly percent. From 2001 to 2005,the verifications of K drought index have done with the independent precipitation and evaporation data,which were not involved in making the drought criterion at four representative stations,namely Urumqi,Yushu,Lanzhou and Xifeng,respectively.The results show that the heavy drought areas are located in south Xinjiang,west Gansu and west Qinghai,the moderate drought areas are located in southern part of north Xinjiang,north and east Gansu,north Ningxia,southeast Qinghai and north Shaanxi,and the light drought areas are located in west Xinjiang,south Gansu,west Qinghai and east Shaanxi.The K drought index has a better function of drought monitoring,and the improved Palmer drought severity index has better monitoring effect in arid area,but it has some limitations to monitor drought in plateau area,semi-arid and sub-humid areas.Precipitation anomaly percent has good monitoring effect for light and heavy drought,but it has bad monitoring effect for moderate drought.It is verified again from 2001 to 2005 that the improved Palmer drought severity index has some limitations to monitor drought in Northwest China,but the K drought index has better monitoring effect in Northwest China.