The wavelet transform(WT) is applied to the time frequency analysis of ultrashort pulsed Gaussian beam on propagation.The time resolved power spectrum of the propagating ultrashort pulsed Gaussian beam is obtained,which show the change of the frequency with time in a pulse cycle.The characteristic of the time resolved spectrum is studied for propagation of the ultrashort pulsed beam in free space.The results show that the time resolved spectrum profile of the paraxial pulses has a time delay in comparison with that of the on axis pulses,and the spectrum distribution is unchanged obviously.