Abstract A.method for analyzing variance-stationary random signal is presented. It is des-ignated as signal decomposition method. With the presented method, the trend component series can be obtained from the variance-stationary random signal; the rest of it is zero-mean stationary random signal that can be studied with the parametric model of stationary random signal. This method, simple and commonly used, is the general method to process the signal. The trend component series derived from this way can near more exactly the trend component curve of the variance-stationary random signal.