Relay technology plays an important role in wireless communication as an effective method to improve network coverage and communication quality. Polarization is an important characteristic of electromagnetic waves. Single-user MIMO multi-hop relay channels show significant polarization selection characteristics, which have a huge impact on the transmission quality of MIMO relay channels. This paper analyzes the channel capacity of a point-to-point single-user polarized MIMO multi-hop relay network and reveals the polarization dependency of adjacent hop channels and multipath propagation links. For a single-user polarized MIMO relay channel network constructed based on the COST 2100 channel model, a hybrid algorithm based on adaptive simulated annealing particle swarm optimization (BSAPSO) is proposed to optimize the polarization configuration of the antenna array, thereby improving the channel capacity of this relay network. The performance simulation results show that the BSAPSO can improve the link capacity of the polarized MIMO multi-hop relay network significantly compared with the other three groups of polarization selection optimization algorithms.