An automatic lawn trimmer includes a case, a battery pack, a controller, a driving device and a trampling device. The battery pack is disposed in the case. The battery pack is configured to supply electrical power to the driving device. The controller is connected with the driving device for controlling the driving device. The driving device is configured to drive the automatic lawn trimmer to move autonomously on the lawn. The grass on the lawn is trampled by the trampling device as the automatic lawn trimmer moves on the lawn. Through regular trampling the lawn, the grass on the lawn is kept at a certain height to realize the beauty and ornamentality of the lawn. The automatic lawn trimmer overcomes the shortcomings of large noise, the difficulty of cleaning up the grass, and the hard work by the existing lawn trimmers.
