Abstract: Due to the original design of the third generation nuclear power plant, the depressurization pathway of the containment integrated leakage rate test is directly leading to the atmosphere outside the containment without the air filtration unit, which may violate the law of radioactive effluents. This defect of design must be solved. After strict technical analysis, a specific technical solution has been put forward, and the corresponding depressurization control manual has been developed following the modification. A successful application has been made during the containment integrated leakage rate test of the refueling outage, resulting in not only overcoming the design defects, but also increasing the depressurization rate comparing to the depressurization rate of the startup test.