Ethane is different from natural gas, crude oil, etc., its critical temperature is low, and it is easy to change phase with the change of ambient temperature. Therefore, it is necessary to increase the constraint condition to ensure that ethane is in the gas phase. Therefore, based on the optimization principle, the calculation model of the economical flow rate of the ethane transport pipeline including the ethane phase, the pipeline stability, and the compressor pressure ratio constraint is established with the lowest annual cost of the gas phase ethane pipeline. Solve the problem with the lowest cost. The gas-phase ethane transmission pipeline proposed in Tarim Oilfield is analyzed as an example. The results show that the economical flow rate of the pipeline under different working conditions ranges from 3 to 7 m/s, which guides the selection of the diameter of the Tarimethane pipeline. The economic design, safe operation and management of the ethane pipeline provide the basis.