Abstract: To transport products in batch process, we generally cut the contaminated interface of gasoline or diesel by two-cut method. For the adoption of one-cut method in gasoline cut, products within different batches are cut in conforming proportions, which can not comply with the requirements of refined management. Relative researches completed with computer simulation and on-site cut testing are made. Results from CFD analysis software on the diffusion process of contaminated section which is brought into purified oil tank indicate that the contaminated sections can be better diffused into the purified oil. Contaminated oil cut testing in a products pipeline clearly shows that a great amount of contaminated oil volume can be reduced and relative handling costs can be lowered by reasonably enhancing the contaminated cut proportions, in particular of the big potential of gasoline cut proportions by utilizing contaminated oil diffusion in the purified oil under the preconditions of a higher quality potential. The calculation methods are recommended to cut proportion in gasoline and diesel oil mixture and illustrates them with actual examples.