Abstract: The comparison on the gas displacement programs of gas pipeline commissioning is made. The 4 gas displacement programs coming from a combination of nitrogen separation and pigging separation are analyzed to determine an available nitrogen separation program for the commissioning of Anping-Ji'nan Gas Pipeline (255 km in total length, 711 mm in diameter). The demonstrations in nitrogen injection procedure and its process, the parameters of nitrogen injection and its distribution of survey points and safety operation steps are made, which is characterized by advantages in technology, safety and reliability and economy.