Abstract: In case that the mixed oil treatment method of offloading from the intermediate station along the line and cutting at the terminal station of pipeline transportation is adopted for the product oil pipeline, the mixed oil offloading from the intermediate station would disturb the development of the mixed oil section along the line, and thus the distribution of mixed oil becomes more complicated. For this reason, a one-dimensional mixed oil prediction model was constructed by analyzing the oil mixing mechanism, introducing the effective diffusion coefficient, and comprehensively considering the law of mass conservation and Fick's laws of diffusion. Meanwhile, ignoring the influence of terrain on oil mixing ignored, the change of mixed oil along the whole line was predicted and calculated under the condition of offloading from the intermediate station and mixed oil backfeed at 0, 40 m³, 60 m³ and 70 m³ in an actual pipeline. On this basis, the influence rule of offloading from the intermediate station on oil mixing along the line was analyzed. The results indicate that offloading the mixed oil from the intermediate station does not affect the concentration distribution of mixed oil. Offloading the mixed oil from the intermediate station reduces the cutting amount of mixed oil in the terminal station of pipeline transportation, but it increases the total amount of mixed oil in the whole line. The change range increases with the increasing of mixed oil offloaded from the intermediate station. Hence, the mixed oil is fed back to reduce the quality of oil in the whole line. Generally, the research results could provide reference basis for the preparation of offloading and cutting scheme of mixed oil in the product oil pipeline for batch transportation.