Abstract: The generalized S-transform with variable-factor is a new time-frequency decomposition method, which is more practical than the traditional S-transform and the generalized S-transform developed by Mansinha.When the scale of the gaussian window function varies with the frequency, the existence of the variable-factor makes this variation have goals, rather than simply narrowing as frequency increasing.This transform can improve the frequency resolution or the time resolution of the local band with purpose, especially the low and high frequency band.A time-frequency filtering method based on the transform is developed.Through filtration of synthetic seismic records, the result proves its effectiveness.