利用部分相干光的相干与偏振的统一理论和2×2交叉谱密度矩阵传输规律，推导出随机电磁涡旋光束经圆环衍射后偏振度的计算公式。在这些理论基础上，研究了随机拉盖尔高斯光束在传播过程中偏振度的变化。分析表明，部分相干涡旋光束经圆环衍射后偏振度将发生变化，在衍射场中光束的偏振度分布情况与入射光的相干度、入射光束的拓扑电荷数、衍射孔径的大小等因素有关。

With the help of the unified theory and polarization of partially coherent beams, and the propagation law of the 2×2 cross\|spectral density matrix, the general formula was derived to calculate the degree of polarization for a class of stochastic electromagnetic vortex beam transmitted through a circular ring. Based on these theories, the changes of degree of polarization of the Laguerre\|Gaussian beam and its propagation characterization have been investigated. It is shown that the degree of polarization will change after the beam transmitted through the circular ring, and the degree of polarization of the diffractive beam is related with the coherence, the topological charges of the source, and the size of the circular ring.