Aiming at the current limitation which is only a single model is used in the optimization of PI controller parameters in HVDC systems, a method to tune the parameters is given.According to the transfer function model built firstly, the stability boundary locus is plotted.Then the small-signal model of system is established.After verifying the correctness of the model, the region which accords with the asymptotic stability of the system is found.Finally superpose the set satisfying the stability margin, and then the PI parameter set address both of the performance requirements is found out.The electromagnetic transient model is built and simulated in PSCAD/EMTDC.The results show that the stability margin and asymptotic stability of the system can be taken into account by this tuning method.