A power adjustment system and a power adjustment method of an autonomous mobile device are provided. In the power adjustment method, two first current control signals respectively transmitted to two drivers are outputted by a control module. A tilt angle of the autonomous mobile device is detected by an inertial measurement module. A travel route is planned by a navigation module, and the control module obtains a steering angle of the autonomous mobile device during a traveling process. According to different weight values of the autonomous mobile device stored in a database module, a weight of the autonomous mobile device is estimated by the control module. According to the two first current control signals and the weight, the steering angle, and the tilt angle of the autonomous mobile device, two second current control signals respectively transmitted to the two drivers are outputted by the control module.