Laser beam quality evaluating is a classical issue in laser optics field. Several beam quality factors have been proposed and utilized. Nevertheless, there have been no standard methods for characterizing and diagnosing laser beam quality. In addition, with the development of coherent beam combining technique, there is no uniform beam quality factor to evaluate the coherently combined beam. In the present paper, several beam quality factors that already exist are summarized and discussed briefly, then beam propagation factor (BPF) as a universal standard for evaluating high energy beam quality is introduced and studied in detail. The physical principle and the measuring technique in practical engineering are briefly introduced, and the universal characters for evaluating single laser beam and coherent combined beam are analyzed. Numerical calculation results show that BPF is fit for evaluating high energy beam quality due to its advantages in perspicuous principle, handy-for-measuring and all-purpose in application fields.