The invention discloses a hydraulic stretching mechanism of a press. The hydraulic stretching mechanism consists of a machine tool body, a cylinder, a one-way valve, an oil pump, an oil filter, an oil tank, a one-way throttling valve, an overflow valve, a motor, a machine tool frame, an oil valve and a machine tool beam. The hydraulic stretching mechanism of the press is provided with the machine tool frame, the machine tool beam and the machine tool body; the cylinder is arranged below a workbench of the machine tool body; the oil inlet and the oil outlet of the cylinder are connected with the one-way valve and the overflow valve by using tee joints respectively; the overflow valve is connected in series with the throttling valve, and one end of the throttling valve is introduced into the oil tank; and the one-way valve is sequentially connected in series with the oil pump and the oil filter, one end of the oil filter is introduced into the oil tank, and the oil pump is connected to the motor.