For the purpose of improving the reliability and satisfying the stage construction requirements of the ?500 kV Xiluodu-Guangdong Same-tower Double-Circuit HVDC Transmission Project, based on its characteristic of sharing common start point, end point, and converter station, and with the incorporation of the system control plan of ordinary HVDC projects, a study is carried out to analyze and compare the system operation mode, DC control system structure as well as function configuration of the project. This paper emphasizes on the control system differences between the ordinary HVDC projects and the aforementioned one, in which the hierarchical structure, function configuration, principle and strategy of coordination control in double-circuit DC system are studied. The optimization measures for the DC system operation mode is proposed, mainly introducing the coordination control and standby function of the two poles, and isolating the two circuits. The research result will serve as a guide for the design, implementation, operation and maintenance of the control and protection system of such a project.