Abstract: In this paper, mathematical models are established on the basis of theoretical analysis of steady-state flow and consist of equations of mass conservation, momentum conservation, energy conservation and state equation for real gases. Based on the four-step Ronge-Kutta method, general numerical simulation program of the model is developed, and has been applied in the calculation of Shanganning-Beijing long-distance gas pipeline. Finally, final section line-packing of long-distance gas pipeline is studied.