Abstract: Based on the precipitation data from 73 weather stations in Beijing, Tianjin and Hebei province from 1961 to 2009, the characteristics of drought and flood were analyzed with methods of a trend analysis and a wavelet analysis. The results indicate that Z index of the annual precipitation is in a decreasing trend in recent 49 years and there exists multi-time scale characteristics. The cycles are 7years, 9 years and 15 years. Z index of summer precipitation is also in a decreasing trend and its cycle is 15 years, while Z indices of other seasons are in increasing trends and the significant cycles are 10-11 years.

Key words: Z index of precipitation, Multi-time scale, Wavelet analysis, Hebei province