Abstract: In the application of laser, the technique of beam shaping was used to modulate the beam to expected intensity distribution. The development of micro electronic and mechanic system provided a solution. The beam shaping was realized by the using of micro mirror array. Based on the idea of randomization, an algorithm was proposed for the application,and the performance under different unit numbers and different noise levels was analyzed so as to present valuable reference in practical application. At the end, a practical optical system model was built and beam trace was performed, and the results under single-mode Gaussian beam and with-noise beam were given. The analysis on results show that beam shaping is achieved effectively using micromirror array under different inputs. And because of the independent addressing property of the micromirror array, the method has flexibility which can satisfy a variety of application requirement.