Abstract: The experiment on pigging operation is carried out in horizontal multiphase flow test loop, of which the pipeline is 350 m in length with 80 mm in inner diameter. The test loop, data acquisition system and experiment methods used for the pigging study are introduced. The pigging operation is a transient flow process. Some important parameters are measured, such as pigging time, sweep-out inside the pipeline and the changing of pig moving velocity. Besides, the average liquid holdup in the test loop is calculated. The changing rules for each flow parameters, pressure as well as pressure difference along the pipelines are analyzed. Some important conclusions are obtained in the experiment, which is significant for the design and management of multiphase flow pipelines.