Abstract: In multi-product pipelines, the flow varies with time, which is decided by the pumping number, resistance and elevation. The variation of flow must generate with the movement of mixed contamination plug in the pipeline. The pipeline always operates under a kind of combined regime of pumps. During a period of time, there are one optimum combined regime of pumps and operating parameters. Under the basis of the analysis of multi-product pipeline system, mathematical model of optimum and method of solving are developed. The goal of optimum operating can be attained, through the optimum seeking of operating manner, combined regime of pumps and operating parameters.