Based on the principle of diffraction for circular aperture, a comparison of characteristic between Fresnel diffraction and Fraunhofer diffraction is made. Integrating with light-intensity Airy disc distributing char. acteristic of Fraunhofer diffraction, a measurement method of laser beam divergence angle based on Fraunhofer diffraction is proposed. By collecting, analyzing and disposing far-field laser facula on the basis of arranging la. ser target, the real test values of laser beam divergence angle are gained. The test result shows that more precision can be got with the method. And the factors influencing on measuring precision are analyzed. The method will af. ford a scientific guidance for laser parameter outfield measurement.