An optical display system, a control method, and a display device, relates to the field of display technology. The optical display system comprises a display screen a first light splitting unit disposed at a display side of the display screen; a first imaging unit comprising a light splitting film disposed at a light-incident surface of the first imaging unit; a second light splitting unit disposed at a light emission side of the first imaging unit; a phase modulation unit disposed at least in a light path from the first imaging unit to the second light splitting unit; wherein, the first-type polarized light transmitted from the first light splitting unit is transmitted from a light emission side of the second light splitting unit, after being turned back multiple times between the first imaging unit and the second light splitting unit.