基于菲涅耳衍射积分方法、Stokes参量和复Stokes标量场，推导了两束单色傍轴矢量光束相干叠加和非相干叠加形成的合成Stokes奇点在自由空间传输时的表达式，研究了合成Stokes奇点在自由空间随振幅比变化的传输特性，同时分析了振幅比对合成Stokes奇点的偏振度的影响.结果表明：在自由空间传输时，合成Stokes奇点的数目、位置和奇点指数受振幅比影响.相干叠加场中，合成Stokes奇点的偏振度始终为1.在z=0面上，当振幅比η≠1时，C点、S23和S31奇点的奇点指数会发生反转；在z>0面上，产生奇点指数加倍的S23奇点.非相干叠加场中，合成Stokes奇点的偏振度小于1且随振幅比发生变化.在z>0面上，随振幅比η的改变，会产生不稳定的V点，V点会重新分裂为S23奇点和旋向性发生反转的C点；随振幅比η的进一步增加，S23奇点会湮灭.研究还发现，合成Stokes奇点的奇点指数之和守恒.

Based on the Stokes parameters, the complex Stokes scalar fields and the Fresnel diffraction integral method, the expressions for the composite Stokes singularities versus amplitude ratio η in two coherently and incoherently superimposed paraxial monochromatic vector optical beams were derived. The properties of composite Stokes singularities in coherently and incoherently superimposed vector optical beams with amplitude ratio propagating in free space were investigated, and the degree of polarization versus the amplitude ratio is analyzed. It is found that, during propagating in free space, the number, position and singularity index of composite Stokes singularities are affected by the amplitude ratio of two vector beams. In the coherent superposition the degree of polarization P=1. At the z=0 plane, when the amplitude ratio η≠1, singularity indices of C-points, S23 and S31 singularities may be reversed. The creation of S23 singularity with double singularity index may take place at the z>0 plane. In the incoherent superposition, the degree of polarization P is less than 1 and is variable with η, by varying the amplitude ratio η V-points may appear, which are unstable and split up into S23 singularities and C-points with handedness reversal. With a further increase of ηS23 singularities may annihilate. In addition， the sum of singularity indices of composite Stokes singularities is conserved in the process.