Abstract: This paper uses Crank-Nicolson mode to resolve the transient flow in long natural gas pipelines. Considering the gas consumption law of the city, gas storage in the end sections of long pipelines subject is studied. Finally, the paper uses a living example to analyze the result of study. Owing to the fact that natural gas in long pipeline is transient flow, the analysis method on stable stream can not be used to study the operating condition of pipeline under the low pressure, small volume of flow and short distance transmission mode.