A tool quick-stop device for a lathe has a base, bottom plate, front side plate, rear side plate, right side plate, left side plate, top fixed plate, tool bar, cam lever, buffer spring, cylindrical guide rail, adjusting nut, first locking nut, double end stud, second locking nut, pressure spring, pressing plate, hold-down bolt and pin shaft. The cam lever supports the tool bar before tool falling. When tool falling is required, the cam lever is rotated through external force. When the cam lever rotates over a certain position, the tool bar instantaneously loses supporting force. Under strong pressure of the pressure spring, the tool bar falls the tool with great acceleration and is separated from the cutting region in a short period of time and the cutting root is frozen.