Based on monthly data of precipitation and air temperature at 160 stations for the period 1951-2012 provided by the National Climate Center of China,the Standardized Precipitation Evapotranspiration Index (SPEI),which characterizes drought,was calculated.Then,the Extreme-Point Symmetric Mode Decomposition (ESMD) of this index was performed to investigate the interannual and interdecadal variations of summer drought in Northeast China.The results showed that summer drought in Northeast China during the study period had distinct characteristics of interannual and interdecadal variations.Significant quasi-biennial,5-yr and 7-yr oscillations occurred in the interannual variations of the SPEI in Northeast China,while quasi-17-yr and 22-yr periods occurred in the interdecadal variations.Further investigations showed that two phases (1975-84 and 1994-2008) were relatively dry,with severe drought having occurred during the latter period (1994-2008).Meanwhile,three phases (1953-1975,1984-1994 and 2009-2012) were relatively wet.Based on the Mann-Kendal test,1975 and 1994 were found to be the change-points of the drought and flood trends for the period 1951-2012.