A trigger knife, including a knife housing, a knife holder, a blade, an elastic part, a trigger, a linkage assembly, a connecting plate. When the trigger is rotated outwards, the elastic part is deformed, and the linkage assembly drives the connecting plate to move and enables the knife holder to move to a first blade ejection position. When one end of the blade is lifted, the knife holder is enabled to fit with an inner wall of the knife housing, the knife holder to move to a second blade ejection position, and the connecting plate is fastened onto the knife housing and separated from the knife holder. When the end of the blade is moved down, the knife holder is enabled to move down, the elastic part is restored from the deformation to enable the knife holder to move to a rebound position.