The invention relates to a tester for testing a discount rule of a water pressure of a grouting circle of an anti-water pressure emission-limit tunnel, comprising a pressure chamber, a simulation tunnel, pressurized equipment and measurement equipment, wherein the pressurized equipment comprises a nitrogen cylinder, a control valve, a pressure regulating valve, a switch, a water tank and an air-water exchange tank; the pressure chamber is a cylindrical container, comprising a switch, a flange plate, a support and a pressure chamber sleeve; the pressurized equipment utilizes the nitrogen cylinder combining with the air-water exchange tank for pressurization to provide a stable osmotic pressure for the pressure chamber; the simulation tunnel, a simulation grouting material and stimulation wall rock are placed in the pressure chamber; the diameter of the grouting material can be converted according to test requirements and geometric similarity; and the simulation tunnel can be precasted into be of different shapes and sizes according to the test requirements and geometric similarity. The measurement equipment can realize accurate measurement on pressure and flow rate. The tester can be used for researching the discount rule of hydraulic pressure of the grouting circle of the anti-water pressure emission-limit tunnel.