The invention is a pulse laser for improving output light beam quality, belonging to the field of laser technique, and characterized in that it comprises pumping source, laser gain medium, saturable absorbing device, and mirror, and it changes the radial losses of the saturable absorbing device to be able to effectively prohibit high-order transverse mode and obtain laser output of high light beam quality. Concretely, this can be implemented by changing the radial absorption factor of the saturable absorber or by coating variable-reflectivity film on the light transmitting surface of the saturable absorbing device, etc. and the invention has advantages of: simple and effective, and stable and reliable to operate, and solves the problem that the traditional techniques increase system complexity and reduce system stability.