Based on the change-point theory and methods, the likelihood ratio method testing in the mean and the Schwarz Information Criterion testing in the variance, change points of time series of the river runoff such as the full year runoff, the flood season runoff, the dry season runoff, and the least monthly runoff were recognized for main gauge stations of Guangdong Province from 1956 to 1999.Spatial-temporal location of these tested change points were described in detail, key features of the characteristics variability of time series of the river runoff were concluded on the whole, and furthermore root causes were illuminated for those change points of runofif time series in terms of the mean and the variance.In general, it showed that change point was widely tested in the existence of the dry season runoff and of the least monthly runoff, which the annual value increased significantly and fluctuated remarkably after the change-point time, otherwise of the full year runoff and of the flood season runoff.Furthermore, the change-point location in the mean of the dry season runoff obviously occurred to 1973 and 1980-1981 in the Hejiang River of the Xijiang Basin, the Dongjiang River, Luohe River of Eastern Guangdong coast mainly due to reservoirs adjustment, and the change-point location in the variance of die dry season runoff to 1981 in the Beijiang River, the Hanjiang River, Jianjiang RiveT of the Western Guangdong coast, Zengjiang River and the top water channel of the Pearl River Delta, mainly by the reason of the precipitation of the dry season in large quantity in 1982.However, it occurred to 1972-1973 in spite of different change-point temporal location in the mean of the least monthly runoff, widely in Xijiang River and its streams, Dongjiang River, Hanjiang River, Zengjiang River, and rivers of Eastern Guangdong coast.In particular, change-point in the mean and in the variance were tested in the existence of these four kinds of annual series in the top Beijiang channel of the Pearl River Delta due to change of the split flow ratio on the channel net under the intensely human activities.