The invention discloses a wind power plant grid-connection stability analysis method considering dynamic characteristics of a permanent magnet directly-driven wind turbine generator. The wind power plant grid-connection stability analysis method comprises the steps of S1, building a simplified dynamic model of a PMSG (Permanent Magnet Synchronous Generator) type wind power plant grid-connection system, and acquiring equivalent output impedance of the PMSG type wind power plant grid-connection system; S2, acquiring equivalent input impedance at a grid side of the PMSG type wind power plant grid-connection system by using a Thevenin equivalent method; S3, calculating an output and input impedance ratio Tm of the PMSG type wind power plant grid-connection system; and S4, judging the stability of the PMSG grid-connection system by using an output and input impedance ratio stability analysis principle. From the aspect of frequency domain stability, the wind power plant grid-connection stability analysis method considers main relevant factors of dynamic characteristics of a PMSG, puts forwards a concept of the output and input impedance ratio Tm of the wind power grid-connection system, constructs a specific expression formula of the indicator, and ingeniously uses an Nyquist curve of the output and input impedance ratio Tm to judge the grid-connection stability of the system.