The invention provides a leakage stop testing device for low-pressure loss gas well repair and a testing method. The leakage stop testing device comprises an analog shaft; a crack analog module capable of measuring the flow is mounted at the lower end of the analog shaft; a pressure testing joint is mounted at the top of the analog shaft, and is connected with a plunger pump through an infusion pipe; the plunger pump is connected with a water storage tank through a pipeline; and a pressure acquiring system and a temperature control system are mounted on the pipe wall, near the pressure testingjoint, of the infusion pipe. The leakage stop testing device is matched with crack modules with different crack widths to realize a leakage stop test; during pressure testing, the plunger pump is started after well repair temporary stop pressure well liquid is injected in the analog shaft to acquire the pressure, flow and temperature data in the analog shaft in the testing period in real time; and through analysis of such data as pressure, flow and temperature, the temperature resisting and pressure bearing capacity of the well repair temporary stop pressure well liquid is evaluated, the leakage quantity and the leakage speed of the well repair temporary stop pressure well liquid are tested, the formula of the well repair temporary stop pressure well liquid is optimized, and the leakage stop operation success rate of the well repair temporary stop pressure well liquid in the well repair scene is improved.