The utility model discloses an installing and dismantling tool for a valve plug of a plunger pump. The installing and dismantling tool comprises an operating rod one end of which is used for being inserted in a valve seat of the plunger pump, and the end of the operating rod, used for being inserted in the valve seat, is the insertion end. The insertion end of the operating rod is provided with a sleeve extending along the insertion direction and used for containing the valve plug of the plunger pump. A magnet used for attracting the valve plug into the sleeve is fixed at the bottom of an inner hole of the sleeve. When installed, the valve plug is directly placed in the inner hole of the sleeve, and guided by the operating rod, the valve plug can be directly sent into the valve seat to be installed so that damage to the valve plug caused by the throw-in method can be avoided; when the valve plug is dismantled, the insertion end of the operating rod is inserted into the valve seat so that the valve plug can enter the sleeve, the valve plug is attracted into the sleeve under the action of the magnet, and then the valve plug can be taken out. The entire operating process is convenient and fast, and additionally the valve plug cannot be easily damaged.