Abstract: The formation and variation laws of oil contamination in batch transportation of products oil pipeline are analyzed. The condition for using vibrating densitometer to do inline detection, cutting, and installation is discussed.The existed problems in density inspection system itself and pipeline running are summarized as follows: filter clogging, slug entering into magnetic pump, no pressure compensation, open air setting and the technical causes that the density data from different stations can not be properly compared and inline sampling in different stations are varied. In order to effectively monitor and control the oil contamination volume and increase quality during batch transportation and oil unloading, the technical measures for improving the density inspection system are proposed. The formation and variation laws of oil contamination in batch transportation of products oil pipeline are analyzed. The condition for using vibrating densitometer to do inline detection, cutting, and installation is discussed. The existed problems in density inspection system itself and pipeline running are summarized as follows: filter clogging, slug entering into magnetic pump, no pressure compensation, open air setting and the technical causes that the density data from different stations can not be properly compared and inline sampling in different stations are varied. In order to effectively monitor and control the oil contamination volume and increase quality during batch transportation and oil unloading, the technical measures for improving the density inspection system are proposed.