Abstract: Optimization problem in operation has been put forward for Daqing-Tieling oil loop pipeline which undertook large-scaled technical transformation. By analyzing pipeline's system structure and logical structure of steady-state operating plan, it is thought that optimization problem for steady-state operating condition can be decomposed into two sub-problems which can be resolved in sequence-oil transporting temperature optimization and pump pipe matching optimization. The article introduces a mathematics model and calculation method of these two problems and actual application practice. The method has a certain enlightening and reference value for optimization of other large-scaled industrial system.