Different from the scalar vortex beam (SVB), the vector vortex beam (VVB) has both an anisotropic spatial polarization distribution and a spiral phase distribution, and carries the orbital angular momentum (OAM) related to the phase distribution. Based on the Collins diffraction theory, the OAM density under the paraxial approximation is obtained. The light field of the VVB passing through the aperture-lens system was collected experimentally. The effects of the aperture truncation parameters and the aperture-lens spacing on the light field and the OAM density of the VVB are discussed in detail. The OAM density characteristics of the VVB and the SVB through the aperture are compared. The results show that the OAM has a slower attenuation with the transmission distance after the VVB passes through the aperture-lens system and is less affected by the truncation parameters compared with the SVB. The polarization state of the VVB is not affected by the aperture-lens system. When the truncation parameter is greater than 4.2, the OAM density and light field are not affected by the truncation parameter. The OAM density reaches the maximum value at the focal position of the lens. The research results provide theoretical references for the application of OAM characteristics of VVBs.