The invention discloses a supporting mechanism for a machine tool cutter and relates to the field of machine tool machining. The supporting mechanism comprises a movable base and a supporting part, wherein the movable base is arranged on the bottom side of the cutter and makes flexible motion towards the cutter, and the supporting part is arranged on the movable base; and particularly in the period of reloading a workpiece or in the machine tool stopping period and the cutter returns to a normal position in the machining process, the movable base is extended out to reach the highest position, the cutter is supported on a horizontal axis by the supporting part, and thus the problem that the machining accuracy of the cutter is affected due to the deflection deformation caused by the long-time suspension of the cutter is avoided.