Based on the daily data observed at 111 meteorological stations in Northwest China from 1960 to 2011, the potential evaporation was calculated using the FAO Penman-Monteith model, and then the humid index was derived, as well as the extreme drought frequency. The temporal and spatial variations of the precipitation and extreme drought frequency were discussed in this paper. The results indicated that the precipitation in Northwest China has increased by 0.17 mm per year in the last 52 years. According to the spatial variation of precipitation, the study area could be divided into three subregions including obvious increasing, light increasing and decreasing. The mean extreme drought frequency was 3.8 months per year during 1960-2011, at a decreasing rate of 0.011 months per year. The variation of the extreme drought frequency also showed a spatial diversity and could be divided into three subregions including obvious decreasing, light decreasing and increasing. The extreme drought frequency showed a negative correlation with precipitation and average temperature, and a positive correlation with rainless days.