Abstract: Gas inventory in terminal pipe is one of the short-term peak shaving scenarios of gas pipelines, which depends on the capacity of gas inventory of terminal pipe. Gas inventory capacity in the pipe estimated by steady-state calculation often has certain deviation from actual value, the basic reason is that the calculation method neglects the variation of final flowrate of pipeline with time. For limit conditions and three typical change laws of flowrate at end pipeline against time, dynamic simulation on running process of terminal pipe is carried out with SPS software to accurately calculate the gas inventory capacity in terminal pipe. Results show that the inventory capacity in terminal pipe with stable-state calculation method is 15% to 25% lower than dynamic simulation, which indicates that 10% to 15% deviation given by related documents does not have generality.