In order to damp the low-frequency oscillation of an AC/DC hybrid power grid, a UPFC & DC-SDC integrated control system is proposed. This combines the Unified Power Flow Controller (UPFC) with the DC Supplementary Damping Controller (DC-SDC). In order to make the UPFC & DC-SDC control system have the best control effect, the eigenvalue augmentation matrix of AC/DC hybrid system based on VSC-HVDC is obtained from the state variables of UPFC & DC-SDC. Based on the matrix, the eigenvalues of small signal probability are calculated of multi-operating modes. The objective function is to minimize the weighted sum of the real part of the probabilistic eigenvalue. Considering the eigenvalue augmented matrix damping ratio, transmission limit and safety voltage constraints, an optimization equation for determining the parameters of the UPFC & DC-SDC integrated control system is constructed and solved by a particle swarm optimization algorithm. Taking the CEPRI36v7 system as an example, it is verified that the control strategy can damp low-frequency oscillation without restricting DC transmission capacity. This work is supported by National Key Research and Development Program of China (No. 2018YFB0904503) and Scientific and Technological Project of Guangdong Power Grid Co., Ltd. (No. GDKJXM20180125).