The invention provides an unloading mechanism of a machine tool. The unloading mechanism of the machine tool comprises a receiving hopper and a conveying belt, wherein the lower end of the receiving hopper is connected with an unloading pipeline; the conveying belt is located below the unloading pipeline; the receiving hopper and the unloading pipeline are installed on a horizontal pushing mechanism through a supporting seat; the horizontal pushing mechanism comprises a pushing air cylinder and two parallel guide rods; the supporting seat is installed on the guide rods through guide sleeves; the pushing air cylinder is connected with the supporting seat. The unloading pipeline is provided with an inclination pipeline and a vertical pipeline connected under the inclination pipeline, and a conversion structure used for converting a workpiece from a vertical state to a horizontal state is arranged in the unloading pipeline. By means of the unloading mechanism of the machine tool, the machining position can be avoided when the workpiece is machined. After machining, the receiving hopper is moved to the position below a spindle through the pushing air cylinder for unloading, and the workpiece falls down along the receiving hopper and a receiving pipeline, falls onto the conveying belt of the machine tool after the posture is changed through a plate part and finally is conveyed out through the conveying belt. Automatic unloading of the machine tool is realized.