Abstract: General situation of West Oil Product Pipeline and mixing mechanism for different oil products formed during batchtransportation process and distribution law of contamination concentrations are described. The paper analyzes primary factors resulting in the increase of contamination volume of the pipeline, including initial contamination and station-passed contamination, variation of flow velocity, differences of viscosity, shut-down and rugged topography. It is considered that the pipeline under slackflow condition as well as contamination formed from sharply rising of flowrate is different from that in plain areas under full flow condition. In allusion to the characteristic of the pipeline with complicated landform and relief, measures to reduce contamination are presented in facets of design of relief system, application of reducer pipe, increase oil products' flowrate and schedulingtransportation sequence rationally.