Abstract: The plume field of the ammonia,leaking out of a space station,was empirically approximated,mathematically modeled,numerically evaluated in direct simulation Monte Carlo(DSMC) method,and theoretically calculated by analytically solving the collision-free Boltzmann equation.The influence of the space environment and leak-hole diameter on the plume field distribution was investigated.The simulated results show that the leak-hole diameter has a major impact.To be specific,as the leak-hole diameter increases in a steady state,the average pressure and gas density increases;a decreasing axial pressure distribution and a symmetric radial pressure profile show up.Depending on the hole-size,the gas density has a decreasing axial(vertical) distribution.The simulated results and analytical solution were found to be in good agreement.We suggest that the simulated and calculated results be of basic and technological interest in leak detection of space station.