针对涡旋光束复用传输中拓扑荷测量的问题，根据广义惠更斯菲涅耳积分，利用傅里叶光学分析方法和光束分步传播法，建立光束传播模型，对拉盖尔高斯光束经复用在真空中传输进行数值仿真。通过分析光束真空传输后的相位分布，发现两束光复用后的相位分布特征与参与复用的各光束拓扑荷值之间有可辨别的关联，具体规律是相位的中心扇叶片数和叶片旋转方向与复用光束中拓扑荷绝对值较小的光束相同，而相位的外边缘相位叉点的个数和旋转方向分别与复用各光束的拓扑荷数值差的绝对值﹑拓扑荷数值较大者相同。所得结果为涡旋光束拓扑荷数的测量提供新方法。

To solve the problem of topological charge measurement in vortex beams multiplexing transmission, a beam propagation model is established based on the extended Huygens-Fresnel diffraction integral, the Fourier optics and split-step beam propagation method. The multiplexing transmission of Laguerre-Gaussian beams in vacuum is numerically simulated. Analysis of the phase distribution after the transmission in vacuum shows that a recognizable association exists between the phase distributions after two beams multiplexing and the topological charge of each multiplexing beam. Specifically, the number and the rotation direction of the central fans are the same as the smaller absolute value of topological charge, while the phase fork of external rim is equal to the difference absolute value of topological charge of each multiplexing beam, and the rotation direction of the external rim is the same as the one with bigger absolute value of topological charge. Therefore, the phase distribution can be used as a new method to measure the topological charge of vortex beams.