Abstract: In laser applications,it is a very important problem to define the beam quality of the laser beam,especially for the multi model laser beam.In general, M2 factor is a useful parameter relative to divergence angle and waist diameter of laser beam.If we determined M2,the beam quality parameters of the practical beam,defined with second order moments,would determine.In practice,the precise measurements of these second order moments are difficult.This paser emphasized that beam parameters defined with energy distribution of beam profile are satisfied with ABCD law for stable cavity solid laser,because the output beam is the sum of multi orders of Gaussian lights.The experiments and analysis are well agreeable.