The invention discloses a mode of mounting a main pump inlet one-way valve seat, which comprises the following steps: 1), placing the valve seat in a valve chamber, and placing an object capable of pressing the valve seat downward on the valve seat; 2), mounting a thin jack on the object capable of pressing the valve seat downward; 3), mounting a nut, a screw and an object connected with the screw for supporting the upper part of the valve chamber on the thin jack, and adjusting the nut and the screw to allow the object supporting the upper part of the valve chamber to support the valve chamber without leaving any movement space; and 4), adjusting the travel of the thin jack, wherein the lower part of the thin jack moves downward to press the valve seat into a required mounting position through the object pressing the valve seat downward. The invention also discloses a mounting tool for implementing the mounting. Compared with the prior mounting art, the mounting mode of the inventionhas the advantage of a labor-saving, safe and simple mounting process due to the fact no tool such as a hammer is used.