Compared with conventional head-up displays (HUDs), augmented reality HUDs (AR-HUDs) can display richer information, and an ideal AR-HUD requires the display of multiple virtual images at different depths to present basic and interactive information. In most traditional solutions, however, the display of information at the two depths is achieved by rotating the reflective mirror at high speed or using the optical zoom system, with lower reliability and potential safety hazards. Therefore, the optical off-axis reflective structure is proposed to achieve the dual-focal-plane display using two picture generation units (PGUs) and a single free-from surface mirror. By adding a plane mirror to increase the object distance of the far-field optical path, we achieve a display of two focal planes. Finally, a dual-focal-plane HUD is obtained, with an eye box of 130 mm×50 mm, field-of-view angles of 5°×1° and 10°×5°, and virtual image distances (VIDs) of 2.5 m and 7.5 m. The research results meet the requirement of the simultaneous display of near-field basic information and far-field interactive information, and the display effects of depth of field are enhanced.