Based on the data of day-by-day precipitation during 1961—2005 from four meteorological stations over Bole region(called Bortala Mongolia Autonomous Prefecture for short), Xinjiang, the thresholds of extreme snow and rain are measured by the method of threshold detection as well as the variation features about the frequencies of precipitation for various grade and the events of extreme precipitation are analyzed by methods of the climatic tendency coefficient, the Kendall-τ rank and order correlation and the successive running t-test etc. The results show that the spatial distribution of extreme precipitation threshold is basically consistent with that of annual precipitation in Bole region, that is larger in the Mountains than that in the Basins, and with obvious regional differentiation. The precipitation days less than 0.2 mm·d-1 during March to October decreased strikingly in large area in these years; the increase of annual precipitation varied among regions. ①For the Aibinur Lake watershed where the annual mean precipitation is about 100 mm, the increase of annual precipitation was mainly caused by the increase of frequencies of moderate rain and light snow, while the frequencies of wet days for the other grade, no matter snow or rain is, displayed an insignificant increasing tendency. Such small increase cant change the nature of arid region. ②For the upper reaches of the Bole River, the annual precipitation was mainly due to the increase in frequencies of light rain, heavy rain and the increase in intensity of moderate rain in summer, and due to the increase in frequencies of slight snow, heavy snow or the extreme snow and the increase in intensity of heavy snow and torrential snow in winter. Such increase pattern easily brings about snow disasters in winter and floods in summer. ③In the middle reaches of the Bole River, the increase of annual precipitation was mostly caused by the increase in frequencies of slight snow, moderate snow and the heavy snow (or extreme snowfall) and the increase in intensity of light rain. The decreasing tendency of the precipitation frequency less than 0.2 mm·d-1 was more sharp than the rising tendency of precipitation in other grades. This precipitation changing mode is favorable for the events of extreme drought in spring and summer on the background of the warming of regional climate.