A general load flow calculation method for power systems with unified power flow controller (UPFC). On the premise of satisfying the control objectives of UPFC, the calculation method combines the power injection model with the Newton-Raphson algorithm to solve the load flow of the power systems by iteration. It is applicable not only to a conventional UPFC structure, but also to a novel UPFC structure wherein the series and shunt transformers of a UPFC are connected to different AC buses or there are more than one series branch connected to a UPFC. The present invention provides the detailed process for performing a load flow evaluation, and it shows that it is unnecessary to add new state variables when solving the load flow by this method, the dimension of the Jacobian matrix will not increase during the iteration.