The invention discloses a method and device for intelligent light modulation of LED street lamps. The device comprises a client computer, a server, a controller, a power supply box type transformer substation and LED drivers. The method using the device is as follows: first of all, the client computer issues a light modulation command, the command goes to the controller via the server, the controller converts the light modulation command into on-off information with different frequencies, and the LED drivers analyze the on-off information to obtain PWM duty ratio information corresponding to the light modulation command for light modulation. According to the invention, the light modulation difficulty of the street lamps is reduced, the workload of management personnel is reduced, and the maintenance cost is decreased at the same time.