The contradiction between AC/DC interconnected power grid and independent calculation mode adopted by regional control centers， brings in various drawbacks to the analysis and monitoring of a power network. To solve these problems， a distributed power flow algorithm for AC/DC interconnected power grid is proposed. The method is based on asynchronous iteration mode. The algorithm applies to two-terminal HVDC transmission systems taken as tie lines. A DC line is modeled at the two terminal subsystems. Sequential method for AC/DC power flow calculation is used as the interior iteration. During the exterior iterations， a DC line is equivalent to an AC line which is used to construct a fix-point iteration about boundary state variable， the equivalent injection power on the boundary buses is modified gradually to obtain a power flow result for the whole system. The experimental results of IEEE standard systems extended to AC/DC power systems indicate that the algorithm is accurate.