The difference-frequency module is the core component of a tunable terahertz source, and its performance directly affects the efficiency of terahertz wave generation. To increase terahertz output power, 2:1 and 3:1 laser beam reduction systems are designed based on the laser parameters after optical power amplification. This ensures that the spot diameters of the two laser beams are consistent, optimizing the beam combining effect. Polarization calibration is used to maintain horizontal linear polarization of the lasers, thereby fully utilizing the maximum nonlinear coefficient of the crystal. After laser beam combining debugging, the two laser beams can be well combined, and after focusing, a spot with a diameter of approximately 22 μm can be formed, effectively enhancing the difference-frequency effect. Experimental results show that this module has successfully enabled terahertz wave generation.