The interconnection between asynchronous power systems can promote the consumption of clean energy andthe optimization of resources by high voltage direct current ( HVDC) transmission systems. However, the frequencystability problem becomes a potential threat to power systems, which can be considered as a major challenge of thesending power grid. A novel total transfer capability assessment model (FTTC) of H VDCs is proposed by taking intoaccount the frequency stability of sending- end grid. Considering the inertia reserve requirements and frequency stabil-ity constraints of the sending-end grid, the model can produce maximum acceptable TTC of HVDC tie-lines. Moreo-ver, a optimization model of the HVDC tie-line operation is developed by considering the coordination of the HVDCcorrective control and the generation trigger after contingency. Finally, a case study of the modified RTS-79 system isused to verify the effectiveness of the proposed method.