Disclosed are a grass trimmer and a control method for the grass trimmer. The grass trimmer includes: an operating device configured for a user to operate and a grass trimmer device including a grass trimmer head and a motor configured to drive the grass trimmer head. The grass trimmer head includes: a spool configured for a grass trimmer line winding around and capable of rotating around a first axis； and a housing formed with an accommodating cavity configured to accommodate at least a part of the spool and formed with an aperture configured for the grass trimmer line to pass through. When the grass trimmer is mounted with the grass trimmer line, a part of the grass trimmer line protruding outside the housing is defined as an effective part of the grass trimmer line. The grass trimmer further includes: a controller configured to control the grass trimmer head to release a grass trimmer line when the grass trimmer head is mounted with the grass trimmer line and a length of the effective part is detected to be less than or equal to a preset value. The grass trimmer is capable of achieving intelligent and automatic grass trimmer line releasing.
