As the micro-display applied to head-mounted display, the optical system not only suits for the small size of the micro-display, but also provides sufficient eye relief and exit pupil, and it becomes perplex. For settling this problem, a head-mounted display, which combines a hybrid diffractive-refractive eyepiece with a reflective relay system using a liquid crystal on silicon (LCOS) with the diagonal size 18mm, was designed. Basing on a Zeiss (60°) eyepiece, and replacing the doublet of it of a diffractive-refractive doublet, a hybrid eyepiece with 20mm eye relief and 10mm exit pupil was designed. The weight greatly reduced and the optical performance improved of the eyepiece compared with the Zeiss one. Considering the space for illuminating source of LCOS, a reflective relay system was used, which includes a flat half mirror and a concave mirror. The magnifying power of the relay system also makes the optical system suitable for the small size of LCOS. The system is with high performance, sufficient exit pupil and eye relief, and reasonable size and weight in the specific application of head-mounted display.