Abstract: The working process of hyper firing-rate weapon system is analyzed in this paper. On base of that, the physical and numerical models of this system are given using one-dimension two-phase flow theory. Further- more，the changing process of each ballistic parameter of flow field in a barrel is researched using the model. Several conclusions helpful for farther experiment are drawn by means of numerical simulation.

Key words: fluid mechanics , gun , hyper firing-rate weapon , interior ballistic , two-phase flow theory