Based on two typical methods for analyzing nonstationary signals, the wavelet pa cket transform and the short time Fourier transform(STFT), a method named wavelet packet timefrequency analysis(WPTFA) was put forward. Four concepts related to the WPTFA method were defined, which were wavelet packet time frequency compo nent spectrum, amplitude spectrum of wavelet packet time frequency component, wavelet packet timefequency spectrum, amplitude spectrum of wavelet packet time frequency. Energy conservation of WPTFA was proved and the method of using WPT FA was presented. Two examples demonstrated some special merits of WPTFA in iden tifying singularities and other details of signals.