A combiner positioning system for a head-up display (HUD) is provided. The positioning system includes a combiner holder, a pair of control discs, a pair of levers and a driving unit. The combiner holder is connected to the combiner, the levers are connected to the combiner holder and the control discs, and the driving unit is connected to the control discs. When the driving unit drives the control discs to rotate, the levers moves the combiner holder and the combiner. The positioning system enables the combiner's first movement from parking position (storage position) to operating position (display position) and a second movement for angular fine adjustment of the combiner is also enabled after reaching the operating position.