Abstract: Aiming at the calibration test of the fuel pool cooling and purification system (PTR) liquid level gauge in EPR units, a test method based on the principle of the connector was proposed, and a special test device was designed. The results show that the new test method can shorten the construction period of the main line by 40 days, reduce the amount of desalination water by more than 3785 tons, and avoid the risk of running water caused by the filling of the whole pool. This method is with low cost, high efficiency, strong practicability and certain promotion value.