Abstract: Characteristics and solving equations for large-opening model and pipeline model of leakage rate of gas pipeline are introduced. Influence of parameters in opening size and pipe diameter of leak opening on internal pressure of pipe, temperature and gas leak rate of the large-opening model is analyzed. With the increase of ratio in opening size vs pipe diameter (d/D) of leak opening, pressure and temperature of the leak opening, the gas leak rate increases. It is pointed out that the d/D of leak opening can be taken as a judgment condition in engineering calculation. Under the condition of 90%accuracy, the pipe leak model can be used to calculate leak rate when d/D≥0.6 and large-opening model can be used when 0.2<d/D< 0.6.