With the help of main advantage model (MAM) functions,the rainfall series of chinese 100 stations in recent 420 monthes (from Jan,1951 to Dec,1985)were analysed.It was found that there are seven MAMs, among them,the south-north difference MAM is very general.And on the base of the power spectrum of each MAM's corresponding time coefficient, six periods:2~4 monthes,5~7 monthes,9~11 monthes,two years,3.5 years,11 years were found.