At present, the setting value of pressure drop rate of block valve in long distance gas pipeline is often determined according to experience. However, unreasonable value will actually affect pipeline safety operation seriously. Therefore it is crucial to conduct simulation calculation of pipeline pressure drop rate in damaged operating conditions. Applied is the SPS software to establish a pipeline damage model and calculate discharge capacity and pressure drop rate of block valve. The calculation results can provide a basis for determination of the setting value of pressure drop rate of block valve. Conducted is comparative study on effect of different damage locations, size and formation times on the calculation results and study results show pipeline damage size has the largest effect on the max discharge capacity and pipeline damage locations and size has the largest effect on the max pressure drop rate, which can provide guidance for determination of various parameters in simulation calculation and computational analysis on the discharge capacity and pressure drop rate in prediction of damage occurrence time.