Beam combining is a key technology to achieve high-power output of quantum cascade lasers. Based on the polarization characteristics of lasers, the experimental principles and methods of polarization beam combining were studied. The polarization beam combining device was composed of a wire grid polarizer and a mid-wave half-wave plate to perform polarization combining of two 4.05 μm quantum cascade lasers. The transmission rate of the mid-wave half-wave plate to 4.05 μm laser and the relationship between the transmission rate and reflectance of the wire grid polarizer to 4.05 μm laser and the angle of incidence were tested. When the angle of the wire grid polarizer was 30°, the transmittance was 81%, the reflectivity was 91%, and its beam combining efficiency reached about 86%. The beam quality after combining was tested and analyzed by a beam quality analyzer. The results show that the beam after beam combination has better beam quality under the condition of ensuring beam combination efficiency.