Fine vacuum diaphragm pump

The invention relates to a high-vacuum diaphragm pump, stabilizing vacuum environment when the diaphragm pump is sucking hydraulic fluid and supplying pressure requirement when discharging hydraulic fluid, which comprises a cylinder body and a oil pool cylinder. The cylinder body is provided with a pressure-fluid inlet valve and an outlet valve, the diaphragm and a support bracket are provided between them, the said piston presents a echelonment shape, the oil pool cylinder communicates with a cavum between the piston and the piston cavity via a compensator valve, the cavum between the piston and the piston cavity communicates with the diaphragm oil pressure cavity via a pressure control valve. The invention can ensure reliability service of the pump while state of stable fine vacuum suction ability is maintained.