Traditional beam-quality measurement methods face problems such as excessive time consumption and low efficiency of optical field information acquisition on the equidistant propagation plane; to combat these, a non-equidistant and bidirectional propagation method to determine beam quality is proposed. A non-equidistant and bidirectional propagation model is established by updating the condition of non-equidistant propagation step, while the iteration of the propagation step in the fitting of laser propagation profile is realized to determine beam quality. Experimental results show that the error of beam-quality measurement is ±1.9% in the non-equidistant and bidirectional propagation model. The proposed method can effectively improve the efficiency of laser beam-quality measurement.