Abstract: By using the standardized precipitation evapotranspiration index（SPEI），the dry-wet climate changes on the 3-month time scale in the past 55 years were documented based on monthly temperatures and precipitation data from 1961 to 2015 from 55 meteorological stations in Xinjiang. The results are shown as follows：（1）The analysis of SPEI-3 on dry and wet change rates every 10 years suggested a weak trend of dryness，with a change rate of 0.055. The dry and wet change rates varied at different sites with the maximum wet rate of 0. 229 and the maximum drying rate of 0. 400. （2）There existed an alternating period of drought and drought relief from 1961 to 1987 and a drought relief period from 1987 to 1996. The severe drought occurred in 1997 and 2008，with the proportions of drought sites of 82% and 78%，respectively，under the threshold R1 = -0.20，-0.30，-0.40. The drought intensity and the duration of drought reached the maximum in 1997. （3）The maximum EOF1 feature vector value was 0.150，reflecting that the overall dry and wet changes were weakening and tended to become dry in the study area. EOF2 and REOF2 showed reverse changes in northern and southern Xinjiang，with the maximum feature vector values of 0. 210 and 0. 250，respectively. The linear trend indicated that the drought was increasing in northern Xinjiang，while the trend of drying out was weakening in southern Xinjiang. EOF3 and REOF3 were in the opposite distribution form. The maximum feature vector value was 0. 320， suggesting that the east Tianshan tended to dry out，while the western South Xinjiang showed a drought relief trend.

Key words: dry and wet change, empirical orthogonal function, SPEI index, temporal sequence, Xinjiang