Automatic extraction and delineation of individual tree crown using airborne laser altimeter is an effective method to obtain forest information. The airborne laser altimeter can describe characterization of vegetation canopy structure by recording the time history of the return waveform within a small footprint for each laser pulse, but difficult to give out the large canopy metrics, like the canopy size and stem diameter. A collection of individual waveforms combined within a synthesized large footprint was used, through Gaussian decomposition of laser altimeter waveforms, to define three metrics: canopy height, canopy reflection ratio, and height of median energy. All three metrics were tested for reproducibility, the results show that combining several individual small-footprint laser pulses to define a composite “large-footprint” waveform is a possible method to depict the vertical structure of a vegetation canopy.