Abstract: A multi-infeed AC/DC hybrid system has the characteristics of strong nonlinearity and strong coupling, and the rapidity of DC adjustment has higher requirements on the determination time of the control strategy. For a weak receiving-end system, the transmission capabi1 ity of the DC subsystem is weak, and the power adjustment range is small, when the fast power regulation is implemented, the system is prone to out of bounds. Therefore, more refined control strategies are needed. In order to control the security characteristic from a macroscopic perspective and realize the fast power fine regulation, the concept of decoupling security region is proposed. As for the weak receiving-end system and multi-infeed AC/DC hybrid system with static var compensator（STATCOM）, based on the decoupling security region, the power regulation problem is transformed into a linear programming problem, and the safety control strategy is quickly obtained, so that the purpose of the fast power regulation of the DC system is realized. Finally, the feasibility of the proposed method is verified by case studies.