Abstract: An elliptical Gaussian beam, which is from single transverse mode semiconductor laser diodes, can be approximated dealt as circular beam because most elements of optical systems generally consist of circular aperture, like lens, illuminator, reflector, etc. By choosing both proper aperture and distance, the laws of reflection and refraction, ray tracing techniques, etc. from geometrical optics provide a foundation for design of laser beam controlling systems. Applications of these techniques to design an axis-symmetrical beam quality controlling systems are presented in this paper, and measurements with Photon 2 350 Beam Profiler are represented. The angle of divergence is corrected within 1mrad, thus the theories in this paper are proved to be applicable to beam quality controlling system.