A novel bi-directional iteration based algorithm is proposed for power flow analysis of AC/DC interconnected power system.The complete electrical circuit models of AC and DC transmission system are used.Specifically，the vector of AC current over convector transformer is defined as coordinate variable with which both of the AC system and DC system modified power flow equations are established separately.Then，the normative correction equations of AC system and DC system are deduced via linear transformation respectively.Subsequently，the bi-directional iteration algorithm is achieved by forward calculating the AC system variable increment and backward calculating the DC system variable increment.This algorithm effectively preserves the convergence of unified iterative method mathematically;it also achieves the flexibility of DC system control mode variation as alternate iterative method.Finally，studies on a typical AC/DC test system and a large-scale AC/DC interconnected power system in South China network indicate the validity and practicability of this algorithm.