Abstract: In the actual operation of complex wet-gas gathering pipeline network, if the pipeline operation pressure and gas transmission volume are higher or lower than the designed values, the calculated gas transmission efficiency could be larger than 100% or lower than actual data, making it difficult to work out a proper pigging cycle. In order to determine pigging period, work out a rational pigging cycle and reduce pigging frequency, this paper puts forward a new method to determine pigging period by analyzing comprehensively relative gas transmission efficiency, pressure gradient between the beginning and end of pipeline, percentage of predicted loading liquid volume and pipeline volumetric capacity, and flowrate of gas, etc.. The analysis and calculation of previous pigging works of frame pipeline network of Sulige Gasfield by the new method show that the new method matches actual situation in field operation, can determine pigging period of complex wet-gas pipeline accurately, which provides the scientific and effective basis to the determination of pigging period and formulation of pigging program.