The invention belongs to the technical field of diffraction optics and particularly relates to a flow cytometry light beam forming system based on a diffraction optics shaping device. The system comprises laser light sources, the diffraction optics shaping device, a reflecting mirror, a beam splitter mirror and a lens, light that is emitted by the light source of each laser device passes through the diffraction optics shaping device to form light spots that are uniform in intensity, the light spots include but are not limited to rectangular spots, and finally, the light falls on a cell sap flow of the flow cytometry system. Compared with results of traditional flow cytometry light beam forming systems, the results by the flow cytometry light beam forming system based on the diffraction optics shaping device have the advantages that the diffraction optics shaping device is applied to the light beam forming system of a flow cytometry so that illuminating light spots that are uniform in intensity are formed, and energy utilization rate and measuring analysis accuracy of the flow cytometry system can be improved.