By use of the angular-spectrum analysis and the Fourier transform method, a correction method is obtained to describe the propagation of few-cycle pulsed beam with constant beam waist. The correspondingly simple approach, which is developed by a Taylor expansion of the known quasi-monochromatic light-beam solution, can be used to describe the propagation of few-cycle laser pulses with arbitrary temporal envelope and transversal profiles. The approximation solution of Gaussian pulsed beam with constant beam waist is obtained, propagation characteristics of the Gaussian pulsed beam are investigated in detail, and effects of some different spectra on pulse propagation are analyzed.