Abstract: Gathering pipeline system circuit of double-pipe mixing light oil is a circuit which is used widely in heavy oilfield. Its primary investment is huge and enormous thermal energy and power energy will be used up during operation period. In order to explore an optimal design scheme, by analyzing the gathering pipeline system circuit of double-pipe mixing light oil, an optimal objective named equal amount annual cost which considers the primary investment and operation cost comprehensively is put forward and a mathematical model is established. A corresponding software has been programmed, which is helpful to the designers of surface planning and design to increase their design efficiency and quality.