Abstract: In this paper, three scenari of the different diameters combination of pipeline to unload oil product are presented in accordance with Lanzhou-Chengdu oil product pipeline with multi-unloading stations. On the basis of analysis of the hydraulic performance in the normal transportation and/or after the unloading operation and comparison of computation results of power consumed, the paper points out that to moderately reduce the pipe diameter has a certain advantage. Meanwhile, the paper analyzes the influence of pipe diameters and transportation ways to the tank volumes, compares the computation results of transportation batches with the products batch at initial and intermediate unloading stations and surplus batch at terminal station at different throughputs, and describes the relations between the pipe diameters and tank volumes.