Abstract: In order to reduce the frequency of false shutoff of the block valve in a long-distance gas pipeline and improve the reliability of the leakage detection system in a valve chamber, the leakage simulation model of a long-distance gas pipeline was established with SPS simulation software by referring to the theory of gas fluid mechanics based on the analysis on causes of a large number of false shutoff events occurred in valve chambers. With this simulation model, the influence rules of the conditions including the leakage location and operating pressure of a pipeline on the process of pressure drop during the leakage of a long-distance gas pipeline was studied, and on that basis, the process data of the possible maximum pressure drop during the leakage of a pipeline was calculated. Then, a judgment algorithm for false shutoff of block valves in a natural gas pipeline was designed, and a control procedure was developed for shutoff of block valves in a leaked pipeline. The simulation data and experimental results show that with the method, the false shutoff signal and the real leakage signal can be distinguished according to the characteristics of pressure change, and the rate of false shutoff of the system could be reduced.