Abstract: Because of the pressure or temperature sudden change, substandard dehydration and untimely pigging and other factors, a gas pipeline is likely to be blocked completely, and consequently its normal operation and smooth gas supply is impacted seriously. The existing blockage locating methods are still in the stage of theoretical analysis and experimental study, and cannot meet the actual needs of the site. In this paper, a certain gas pipeline was taken as an example. The effects of complete blockage on the pressures and flow rate along the gas pipeline, especially 500 m away from both ends, were simulated and analyzed by the simulation software SPS. And the feasibility of the existing pressure or differential pressure transmitters on transient parameters monitoring was verified. It is shown that when the pressures at both ends of the gas pipeline are constant, the pressure in the upstream of the complete blockage increases rapidly due to gas compression while that in the downstream decreases rapidly due to gas expansion. And the pressure waves propagate back and forth along upstream and downstream pipeline sections and the wave crest attenuates gradually. There are no gas flows through the two pipeline sections when the pressure along the both pipeline sections is equal to that at the initial point or the terminal point respectively. The closer it is to the blockage, the more obvious the pressure and flow fluctuation are and the shorter time it takes to reach a steady state. The research results lay a theoretical foundation for the further study of gas pipeline blockage location method based on pressure and flow monitoring.