Aiming to enhance the damping of certain low frequency oscillation modes in voltage sourced converter based high voltage direct current （VSC-HVDC） systems, a coupling robust controller design method based on multi-input multi-output （MIMO） system model is proposed by utilizing the interaction between different control loops. Firstly, the optimal feedback signal is selected by using the dominant mode ratio （DMR） index and then sent to the controller. Then, the total least squares-estimation on signal parameters via rotational invariance technique （TLS-ESPRIT） is used to identify the MIMO system model. Finally, the mixed H₂/H_∞ robust control theory is applied to design the HVDC supplementary robust controller with regional poles placement. A simplified multi-infeed HVDC transmission system is simulated in PSCAD/EMTDC. Compared with the traditional lead-lag compensators without coordination design, the simulation results verify that the designed controller has better control effect and stronger robustness.