Abstract: Mixed oil cutting in Lanzhou terminal of Western Oil Product Pipeline is a key link to enhance the pipeline operation benefits and ensure the quality of downstream oil product. As shown by statistics of mixed diesel oil and gasoline cutting since 2009, the volume of mixed oil cutting in the Terminal has presented a clearly rising trend, therefore, an analyzed on it from three aspects was carried out as follows: (1) the most indistinct problem in mixed oil cutting of the terminal was the density value confirmation for trailing oil product, the cut volume of mixed oil was dependent on the control of density value of oil product at the second cutting point; however, it is difficult to confirm the precise density value of trailing oil product; (2) the standards adopted in determining the differential density value of mixed oil interface for Lanzhou Terminal and Xinbao Station was not be applicable, which rapidly resulted in the raising of one-turn mixed oil volume and (3) oil products stored in outlet tank of the Initial Station was usually in the case of"simultaneous inlet flow and outlet flow", and moreover the oil products were from different refineries, which caused unstable intensity for the front/back sections of pure oil for the initial mixed oil interface with an unclear interface. Measures of improving cutting proportion, correcting density deviation and changing switching mode of oil products in the Initial Station were presented to correct the aforesaid matters in order to effectively reduce cutting volume of mixed oil and achieve excellent economic benefits.