Abstract: Based on radioactive inert gas movement model in gaseous waste management system of EPR reactor type, calculation on the gas movement duration and flow rate parameters were carried out during 1 refueling cycle, regarding to two kinds of system operation modes for the main configurations of purge unit and delay unit. One was steady mode, and the other one was purge gas mode, as well that 28 operation cases of the units were analyzed one by one for the same purpose. The key point of the calculation is to give a result of Kr and Xe delay status during passing the delay unit and to deduce the delay time of the key isotopes. Meanwhile, by combining the system parameters and decay equation, the activity flow rate was finally determined. The methodology and the result will be used as a theoretical basement for the proof of conformance with the Chinese regulatory request.