The invention discloses a pressure control method for a pressure test medium capable of bilateral flow and belongs to the technical field of hydraulic testing. According to the invention, the pressure increasing control process includes closing a water outlet stop valve and an unloading valve, opening a water inlet stop valve, a plunger moving to a front dead center, closing the water inlet stop valve, controlling the plunger to retreat to a rear dead center, advancing the plunger, automatically closing a water inlet valve, opening the water outlet stop valve and performing pressurizing, and repeating the operation until an object pressure is reached; a pressure maintaining control process includes a to-be-tested container requiring no constant pressure maintaining and requiring constant pressure maintaining; a pressure reduction control process includes the to-be-tested container requiring no pressure reduction process control and requiring pressure reduction process control, and when executes control of the pressure reduction process, the pressure reduction control process includes opening the water outlet stop valve, controlling the plunger to retreat, such that the working pressure and the pressure in the cavity of the plunger are equal and slow reduction is implemented during which process the movement of the plunger can be stopped at any time so as to conduct pressure maintaining in the process. According to the invention, the method can effectively execute control over pressure increasing speed and the pressure reduction speed, and has a control precision reaching +-0.02MPa.