Based on contaminated product theory, contaminated product control equation on cold and hot crude oil was established. Using FLUENT, concentration distribution of contaminated product before and after shutdown was analyzed by numerical calculation. So was the impact on the concentration of contaminated product. The results show that the trailing oil product keeps going under the influence of the inertia force after shutdown of the horizontal pipe section, which makes the mixed contamination plug grow with the shutdown time extended. The mixed section is longer if the crude oil from Russian is transported before the oil from DaQing. The mixed section of the vertical pipe is longer than that of the horizontal section. The length of the mixed sections almost the same in both ways, but the concentration distribution of contaminated product is more evenly in the former. The results match well with the actual, which can provide a theoretical guide to practical applications for projects.