Abstract: Slug flow is a common flow form in multiphase flow transportation. To provede a theoretical basis on designing oil-gas separator, the study of the form and development law of slug flow has been carried out. Based on the site measured results got from oil-gas mixed transportation pipeline and the slug flow formed in horizontal, vertical and undulated pipeline section and its development model, the paper puts forward the movement law of slug flow, which is suitable to big diameter and long-distance pipeline. The paper introduces the simulation method on calculating the slug flow in multiphase flow. This method, with a wide applicable scope, can be used to analyze on the transportation of pipelines located at the various terrains. It is pointed out that the variation and development of slug are related not only to the size and velocity of slug, but also to the inclination of the pipeline through analysis on the experimental results, and it is considered that this method can be used to fairly predict the maxmum of slug and its distribution, meanwhile, the paper shows that the simulation method has to be improved, the model remains to be corrected.