Abstract: Based on 48 years of summer rainfall data,Morlet wavelet analysis was done of the sequence of summer rainfall in Nenjiang and Harbin,on a multi-time scale.Results show that in recent years,the summer rainfall in Harbin displayed the most apparent cyclical variation on a 29-38-year scale,the largest modulus,and the strongest energy;and the summer rainfall in Nenjiang did an obvious cyclical variation on a 19-30-year scale,and its energy value is quite large.Both the two cyclical variations showed a trend of being stronger in energy with the time.Presently,both the summer rainfalls in Nenjiang and Harbin are in a long cyclical period of low-water.It is predicted that in a relatively long period the summer rainfall will be lower than the average of the past 48 years.