In fire extinguishing systems, inert gas discharge nozzles are important equipment for rapidly suppressing fire. In particular, it is of importance to find the optimal configuration of nozzle for improving the performance of discharged extinguishing agent. In this study, effects of the port configuration of the orifice tube were investigated to analyze the outflow efficiency of gaseous extinguishing nozzle using the commercial CFD code, ANSYS CFX 17.1. The numerical results of the present study were compared with reference model to evaluate the reliability of the discharging systems.