Optimal load shedding model is an important part of adequacy assessment of AC/DC hybrid transmission systems. In this paper， based on the complex conditions and multi constraints of AC/DC hybrid transmission system and HVDC operation characteristics， an optimal load shedding model is proposed. The polar power-direction coefficient is used in the model as the control variable. The model takes into account the practical issues such as the outage of DC polar due to operation restricting， and the power support and power regulation functions of HVDC of interconnected power systems. Meanwhile， to overcome the convergence difficulties of current primal-dual interior point methods with flat starting， the idea to convert the problem of finding an initial point into that of finding a stable equilibrium point of active-set based dynamic system is introduced， and the pseudo transient continuation method is applied to seek the optimal initial point. The numerical results from the IEEE-RTS 96 reliability test system demonstrate that the proposed approach can provide a novel powerful tool for the adequacy assessment of AC/DC hybrid transmission systems.