Abstract: Due to the numerous components and complex pipelines of the nitrogen system in space environment simulator, there exists deviation between the system parameters designed by the conventional theoretical calculation and the actual operation results, causing flow and pressure of the system deviating from expectations. In order to accurately analyze and determine the key parameters of nitrogen system, the numerical simulation software FloMaster was used to conduct a one-dimensional simulation of a single-phase closed loop nitrogen system. The parameters of a single device model in the nitrogen system were studied to determine the key parameters that affect the operation of the system. Comparing the simulation and the actual operation results of the system, it was found that the flow resistance of liquid nitrogen (LN₂) pipelines was the main factor causing the deviation of the system flow and pressure. Moreover, the variation of LN₂ flow rate would also affect the heat transfer, resulting in a deviation of LN₂ temperature at the outlet of the shroud. Whereas, the system deviation does not affect the trend of changes in the characteristic parameters of the system. In summary, the proposed simulation method simplifies the calculation process of theoretical calculation methods, improves design efficiency, and provides a data foundation and equipment selection basis for system design.