In view of the subsynchronous oscillation with weak damping occurring in Hulunbeier power plant in the Hulunbeier League power system，the subsynchronous oscillation-dynamic stabilizer（SSO-DS）is recommended to suppress the oscillation in this actual project.This paper proposes the subsynchronous modulation of instantaneous reactive power control strategy for SSO-DS.The damping provided by SSO-DS using the proposed control strategy is derived on the basis of the complex torque coefficient method.Relevant factors that influence the size of the damping are presented.And the real-time digital and physical closed-loop simulation platform is developed.In order to suppress the subsynchronous oscillation with weak damping，a method of finding the effective damping area is proposed to optimize the controller parameters.The effectiveness of the control strategy and the accuracy of parameter optimization are both verified by closed-loop simulation and field experiment.