Because of its intrinsic topological charges (TCs), a vortex beam offers a Hilbert space with a higher dimension when it is utilized as a carrier of space optical communication. As a result, optical communication based on vortex beams enjoys significantly improved channel capacity and security. At the channel receiver in optical communication, TCs need to be identified accurately and rapidly to decode the transmitted information. In this paper, the dimension of polarization state is introduced into the process of TC identification, and the influence of polarization state on TC identification is studied from the perspectives of numerical simulation and experimental verification. Interference images of a signal beam and a reference beam with different polarization states in a Mach-Zehnder interferometer are analyzed. The results show that the Gaussian beam (reference beam) with the circular polarization state is the most favorable choice for identifying the TCs of the vortex beam (signal beam) with the same polarization state, and these signal beam and reference beam also appear to be least sensitive to the angle of the interference optical path during TC identification. The theoretical simulation is in good agreement with the experimental data, which indicates that the proposed polarization interference-based TC identification scheme provides a reference for future high-speed and high-capacity optical communication based on vortex beams over distances in the order of magnitude of several kilometers.