The invention discloses a sternal distractor comprising two symmetrically arranged distraction plates, the middle of the outer end faces of the two distraction plates are recessed inward to form fixing grooves, a first distraction arm is arranged on the distraction plate located on one side, a second distraction arm is arranged on the distraction plate located on the other side, a first connectingrod is arranged at one end of the first distraction arm remote from the distraction plate, and a second connecting rod is arranged at one end of the second distraction arm remote from the distractionplate. A threaded hole is arranged in the middle of the first connecting rod, the axial direction of the threaded hole is parallel to the length direction of the first connecting rod, a threaded through hole is arranged on the first distraction arm, and a distraction bolt is arranged in the threaded through hole. A support plate is clamped between that sternum, and the second connecting rod is pushed to move by the support bolt, so that the two support plates are moved toward each other, and the sternum is distracted to expose the operation field of view.