Power flow calculation is the basis of all kinds of calculation in power system. This paper presents an AC/DC power flow calculation method based on rectangular coordinate injection current model. Firstly, the mathematical model of AC/DC power system is analyzed. Starting from Newton"s method in rectangular coordinate form, the coupling coefficient matrix of AC/DC system and Jacobian matrix of AC system are transformed to form a modified equation of injection current. The new expression of coupling coefficient matrix of current injection model in rectangular coordinate is obtained. Jacobian matrix is greatly simplified and improved. Convergence improves the calculation speed and efficiency, and the program implementation is simpler, saving memory capacity.