Abstract: This paper studies the diffraction characteristics of a serrated circular aperture with random radius, and puts forward and proves that the aperture can further improve the near-field distribution of the beam and reduce the diffraction modulation in the beam center. The simulation results of the axial diffraction and the intensity distribution in the cross section are given, which shows the diffraction light after this aperture has higher filling factor and lower modulation rate compared with that after the amplitude modulation serrated aperture. The intensity modulation of Fresnel diffraction on the axis is suppressed by using the random radius serrated aperture in larger space. The farthest range of suppression can reach 0.15 m.