The invention discloses an economical dispatching method for an AC/DC (alternating current/direct current) interconnected power grid and belongs to the field of economical dispatching of an electric power system. The method comprises steps as follows: firstly, establishing an optimal power flow model of economical dispatching of the AC/DC interconnected power grid consisting of objective functionsand constraint conditions, and converting the model into an optimal power flow continuous model of the AC/DC interconnected power grid with a fixed conversion transformer's tap changer gear, and performing solving; utilizing the optimal solution of the optimal power flow continuous model as an initial value, restoring an integer representing the conversion transformer's tap changer gear to be a variate, establishing an optimal power flow mixed integral model of the AC/DC interconnected power grid with the to-be-optimized conversion transformer's tap changer gear, and performing solving; finally, recovering AC feasibility to obtain the economical dispatching scheme of the AC/DC interconnected power grid. According to the method, modeling and solving of the AC/DC interconnected power grid are converted into the problem of non-linear optimization of mixed integrals, an iterative computing framework is provided, and the economical and feasible dispatching scheme can be obtained with the method.