For studying and optimizing propagation characteristics of vortex beam,the fundamental theory for generating vortex beam with spiral phase plate is deduced,and the factors of affecting the radius and width of vortex beam spot are discussed in detail.Based on the designed model of spiral phase plate,the propagation process of vortex beam with different topological charges is simulated by the ray tracing software(TracePro) and validated through the experimental platform.The results show that the radius and width of light spot are directly proportional to propagation distance of vortex beam.In addtion,the width can also increase with the increase of the topological charge.At the same time,a new method using the spiral phase plate superposing to get different topological charges of vortex beam is proposed.The theoretic analysis is consistent with the experimental results.The conclusion provides theoretical foundation and practical guidance for the application of optical micro manipulation technology and the obtaining of vortex beam with different topological charges in the experiment.