In order to analyze the static voltage steady state characteristics of a two terminal VSC-HVDC AC/DC system, the AC/DC continuation power flow method is proposed by combining alternating solution method with continuation power flow method. The direction of the load growth is determined by initial solution from the initial input and the load power margin parameter is introduced. The different system load margin is gotten by adjusting VSC-HVDC control strategy, and the left eigenvector multiplier method is used in the system load margin sensitivity calculation. Based on IEEE39 bus system and the IEEE 118 bus system with two terminal VSC-HVDC modeling and simulation, it is concluded that the changing rules of system load margin and load margin sensitivity are approximate linear. The impact of DC power flow on the system load power margin is contrary. The results verify that the proposed method is valid. This work is supported by National Key Research and Development Program of China (No. 2017YFB0902401).