The invention discloses a method and a system for recognizing and expelling animals on towers on the basis of ultrasonic waves. The system comprises a module for regularly acquiring data of pressure sensors, a module for extracting the data and judging the types of the animals on the towers and a module for executing different expelling modes according to the different types of the animals. The module for regularly acquiring the data of the pressure sensors is used for regularly acquiring the pressure data of detection locations; the module for extracting the data and judging the types of the animals on the towers is used for judging whether the animals on the towers are safe tiny organisms or human or dangerous animals by the aid of the pressure data; the modules for executing the different expelling modes according to the different types of the animals is used for expelling the dangerous animals by the aid of the ultrasonic waves and warning the human by means of broadcasting. The method and the system have the advantage that the animals on the towers and non-maintenance personnel can be effectively recognized and expelled by the aid of the method and the system.