Abstract: With the construction of long-distance gas pipeline toward large diameter, high pressure, and high pack shaving requirement, the study of unsteady-state flow is in urgent need.In this paper according to the basic laws of hydrodynamics, the mathematics model, including equations of mass conservation, momentum conservation, energy conservation and SHBWR equation of state for real gases, is established.Based on the implicit central difference scheme, the general numerical simulation program of the model is developed.The program is validated in the Harbin-Yilan gas pipeline.Finally, final section line-packing of long-distance gas pipeline is studied.