对东川蒋家沟发生的一次阵性泥石流序列进行周期性分析。然后根据分析结果，提出了泥石流发生相关的几个问题。

The article intends to disclose the periodic character of intermittent debris flow .We selected a series of observed data that is long enough to be analyzed .The value of element is the interval between two intermittences and the subscript of series is the number of the intermittence , which is different from traditonal time series .Random disturbance was weaken and long time tendency was emphasized by using moving average process .In order to analysis periodie character , discrete Fourier transform is used to convert the series from timedomain to frequency -domain .Then the value of
periodogram was calulated by Fourier coefficient based on their definition .By Fisher statistical test with conspicuous levl α=0.005 We obtain seven periods :130/1 , 130/2 , 130/3 , 130/4 , 130/5 , 130/6 , 130/7(130 is the length of the series). The same analysis to other observed data obtains similar results which implicit periods gather in the ahead location of periodogram .Some reasonable geographical explanations are given in the end of article :1 .Nature condition triggering debris flow is of periodicity , 2 .The movement of debris flow is longly periodic , 3 .The supply of loose material forming debris flow recovers slowly . It is possible that reason implies in the results as dynamical mechanics .