As a result of prosperous development of HVDC transmission, multiple HVDC sending systems have been transmitting power through identical AC tunnels. These tunnels are thus turned into junction areas, interconnecting with multiple HVDC sending systems. Their existed regional security and stability control system strategies are no longer compatible with changed system operation characteristics and issues. Worse still, strategy actions might even introduce risks into operation. To solve such dilemma, this paper produces analysis on operation risk of junction areas of multiple HVDC sending system, proposing a method of region security and stability control system design for these areas according to operation issues. This method has been practically applied in security and stability control system transformation in Huangping area in Yunnan province. The design is proved to be effective for coping with operation risks and it is also suitable to be referred in security and stability control design projects for similar areas.