Abstract: An in-line analysis on the operating data of cut point has been made for the Fushun- Yingkou oil products pipeline. The results showed that the uncomformity existed in each volume of the mixing oil and the mixing length, and the cut point, flow properties, pipeline's characteristics and combination of pumps were all major influence factors. It is pointed out that the low throughput and low flowrate are the main reasons on the high contamination, and the problems can be solved by means of automatic trace of contamination interface, automatic valves and in-line mass flowmeter, and mingling back with oil products.