The utility model discloses a device for testing the water stability of an asphalt mixture. The device comprises a base, a support frame and an insulation box I, wherein an insulation box II is arranged above the insulation box I and is fixedly arranged at the upper part inside the support frame, a flowing water channel I is arranged on one side of the insulation box I, a flowing water channel II is arranged on the other side of the insulation box I, an installing base is arranged in the insulation box II, a sleeve is vertically arranged on the installing base, an opening is formed in the upper part of the sleeve, a water pipe I is arranged on one side of the sleeve, a water pipe II is arranged on the other side of the sleeve, a test piece is arranged in the sleeve, the water pipe I and the water pipe II extend into the sleeve and connected with the test piece, a hydraulic cylinder is arranged at the upper part of the support frame, a hydraulic water pump is arranged at the upper part of the flowing water channel I, a strain sensor is embedded in the test piece, a pressure sensor I is arranged on the lower end of a hydraulic cylinder piston rod, and the strain sensor and the pressure sensor I are both connected with a processor. The device is simple to operate, and is capable of completely evaluating the water stability of the asphalt mixture.