The HVDC transmission system may lead to subsynchronous oscillation under certain circumstances. Based on the complex torque coefficient principle and fuzzy immune control method， a subsynchronous oscillation damping controller is designed. Previous subsynchronous damping control（SSDC） design methods based on linearized system equations are limited by the system's scale for the course of dimensionality problem and it is difficult or even impossible in engineering application to the complex power systems. Thus the fuzzy immune control method is proposed for these reasons. The controller proposed is easy to realize and its parameters are self-adjusted by the fuzzy immune rules to adapt to different operation conditions. Simulation results of PSCAD/EMTDC electro-magnetic programs show the validity of the proposed subsynchronous damping controller.