To alleviate the visual accommodation-convergence conflict and discomfort caused by conventional single-focus plane head-mounted displays while considering factors such as system volume, structural complexity, and cost, this study proposes a polarization multiplexed dual focal head-mounted display optical system based on the single-image generation unit. The system uses the twisted nematic liquid crystal unit and the polarization reflection film to achieve dual focal display. It features an exit pupil diameter of 8 mm, an exit pupil distance of 18 mm, and field-of-view angles of 24.0°×7.5° and 15.4°×4.8°, with the corresponding maximum distortions of -2.57% and 1.71%, respectively. Meanwhile, the focal lengths are 25.8 mm and 41.0 mm. Additionally, this study analyzes stray light in the system and proposes effective suppression measures. The research results indicate that the performance of the dual focal head-mounted display system satisfies the requirements for practical applications.