To suppress the Banding phenomenon generated when the laser beam scanning (LBS) and grating optical waveguide are directly coupled in the head-mounted augmented reality display system and improve the final imaging effect of the system, the Banding phenomenon is first introduced, and the Banding phenomenon is analyzed and discussed. Then, a beam expanding suppression method with a diffuser is proposed, and its feasibility is verified by the beam expanding optical path structure. Aiming at the suppression scheme, the design optimization for the small-size and large-field-of-view relay optical path is carried out to meet its applications in the head-mounted augmented reality display system. The total length of the designed system is less than 25 mm. At the cut-off frequency of 43 lp/mm, the modulation transfer function values of the front-end and back-end fields-of-view are greater than 0.3, and the distortion is less than ±2.2%, which meets the requirements of various indicators of the design. The proposed method can effectively suppress the Banding phenomenon in the process of coupling between LBS and grating optical waveguide. Therefore, this work provides a certain reference value for the research of the head-mounted augmented reality display systems based on LBS and has potential application prospects.