This paper documents how the flow allocation of Shaanxi-Beijing gas transmission system was optimized using TGNET stimulation software, based on criteria of minimum energy consumption. Using Shaanxi-Beijing gas transmission pipeline system as an example, via comparison of different transmission options, it is concluded that for pipeline network system consisting of more than one pipeline, utilizing the pipeline with largest diameter as priority for flow allocation is not always the optimal transportation scheme. Instead we have to take into consideration the overall situation of the loading on each pipeline. In real life production operations, the optimal transmission scheme to achieve the lowest energy consumption has to take into consideration of the flow-rate and loading of the pipelines in the analysis. The conclusion of the research would provide valuable reference for production and operations of similar pipeline systems.