The present invention, belonging to the technical field of dispatching automation of a power system, discloses a power system dynamic state estimation method considering zero-injection constraint. The power system dynamic state estimation method is characterized by solving a power system dynamic state estimation model considering zero-injection constraint by using projection unscented Kalman filtering-based method. According to the power system dynamic state estimation method, zero-injection constraint conditions of the power system are added into a conventional power system dynamic state estimation, comprising a state transition equation and a measurement equation of the estimation model. State prediction, state filtering and state projection are carried out by using a projection unscented Kalman filtering-based algorithm, and finally a state quantity estimated value which meets the zero-injection constraint of the power system is obtained. According to the power system dynamic state estimation method, the problem of inaccurate estimation results caused by no consideration on the zero-injection constraint in the dynamic state estimation process of a conventional power system can be solved, and the obtained state quantity estimated value further accords with a true value, thereby ensuring effectiveness of subsequent analysis and control.