The invention discloses a centralized control method of large-scale electric automobile grid-connected charge and discharge. Firstly a nine-area diagram is divided on a U-mu plane formed by the low voltage side bus voltage amplitude U of an electric automobile centralized charge and discharge station and a power grid load margin index value mu according to the upper and lower limits of the reasonable operation range of two variables, and the control strategy of the corresponding electric automobile charge and discharge behavior of each area is formulated; then real-time operation data closely related to the power grid voltage stability are inputted according to a trained support vector machine optimal model so that the current maximum load parameter prediction value of the power grid is acquired, and the current load margin index value is calculated; and the area of the current operation point in the nine-area diagram is determined by combining the real-time value of the charge and discharge station low voltage side bus voltage amplitude, and then the electric automobile charge and discharge behavior is controlled according to the control strategy of the area so that the voltage stability of the power grid in large-scale electric automobile charging and discharging can be effectively guaranteed, the peak shaving effect can be realized and safe and stable operation of the power grid can be maintained.