Gaussian complex wavelet transform was used in the dynamic frequency spectrum analysis of HT-7 MHD (magneto-hydrodynamic) oscillations. It is shown that this method can provide good temporal resolution and spatial resolution, which is suitable to analyze the dynamic frequency spectrum of MHD oscillations. Typical discharges with sawtooth and MHD instabilities are analyzed with this method. The results show that the oscillation frequency is associated with the plasma pressure gradient.