The invention belongs to the technical field of measurement of destruction range and permeability of a rock mass, and discloses a method for testing a rock mass loosing circle based on action of pressure water of a drill hole. Viewers used in the testing method comprise a testing probe, a drilling machine, a drill rod and a control operation platform, the testing probe comprises a front plugging device, a middle plugging device, a tail plugging device, a converter and a communicating pipe, the plugging device comprises a water leakage pipe and a joint and rubber capsule connected to the two ends of the water leakage pipe, the rubber capsule is wrapped around the periphery of the water leakage pipe and forms a plugging cavity with the water leakage pipe, an outside water source is injectedinto the plugging cavity to expand the rubber capsule, and a water injection cavity is formed with the drill hole. A testing device uses the fact that a plugging high-pressure water source is converted to an observation low-pressure water source, the plugging process and the testing process of a same water source respectively work under the respective pressures, pipelines in the drill hole are reduced to one, the problem of winding of the drill rod and a flexible pipe is solved, and the stability in conversion of the pressure and the propelling measurement efficiency each time are improved.