Abstract: As the scale of long-distance cross-region HVDC transmission continues to grow, the problem of transient voltage stability in power systems becomes more and more prominent. In view of the problem that the existing pra-ctical quantitative evaluation indexes of transient voltage cannot account for the influence of different voltage thresholds and low voltage duration, a transient voltage stability evaluation method considering the sag depth and accepta-bility is proposed in this paper. Firstly, taking into account the voltage recovery characteristics of load nodes, traditi-onal HVDC and flexible HVDC converter station nodes after fault removal, a quantitative evaluation index of transi-ent voltage drop degree considering traditional HVDC and flexible HVDC is constructed. Then, through the refined zoning of the transient voltage drop degree, a transient voltage drop degree index considering different voltage thresholds and low voltage duration is established to achieve a quantitative characterization of the transient voltage drop degree of the receiving system. In order to solve the problem that the traditional transient voltage stability margin i-ndex cannot take into account the influence of network topology, Based on the propagation characteristics of the di-sturbance energy of the fault bus between the other buses with different electrical distances, the transient voltage st-ability margin of the AC/DC system network topology is quantitatively evaluated. Finally, through the simulation an-alysis of a real system, the accuracy and effectiveness of the proposed transient voltage quantitative evaluation meth-od are verified.