The turbo-generator units in the vicinity of HVDC transmission system are vulnerable to Sub-Synchronous Torsional Interactions (SSTI). Based on the AC-DC system decoupling transfer function structure of Generator rotation rate to the electric torque, a novel phase correction method of HVDC supplementary subsynchronous multiple models damping controller is proposed, and a SSDC software for adjusting and analyzing the parameters with matlab is designed. The simulation, including Hulunbier-Liaoning HVDC system in the northeast power grid in China which can arouse the SSTI, proves the feasibility and effectiveness of the method.