Abstract: During the process of on-line pigging operation of long-distance gas pipeline, problems including high flowrate of medium, high wear loss of pig and difficulties in tracing and monitoring are commonly encountered. If the pig travelling speed is not under proper control, plugging of pig or damage of catching devices could happen. According to the actual situation of on-line pigging operation in Ji-Zi Gas Pipeline of Shandong Province Gas Pipeline Co. Ltd., and the calculation analysis of velocity model, the operation conditions of pigging was grasped and parameters of process equipment were adjusted in time to keep pig travelling speed under control. Operation method of secondary pig catching was used and calculation results based on the Newton's Second Law and Law of Conservation of Energy were applied to adjust the travelling speed of pig entering the catcher to ensure the safety of pig receiving. It recommends to study the variation pattern of instant gas quantity in detail in order to control the travelling speed of pig more accurately.