Abstract: A treadmill and an exercise accident detection method thereof are provided. The treadmill includes a treadmill body, an inertial sensor, and a processor. The inertial sensor is mounted on the treadmill body and continuously senses multiple sensed values while a treadmill belt of the treadmill is running. The processor is coupled to the inertial sensor, acquires multiple first sensed values sensed within a preset period by the inertial sensor, and analyzes the first sensed values sensed within the preset period to determine an event threshold value. The processor determines whether multiple second sensed values sensed not within the preset period by the inertial sensor satisfy a normal condition according to the event threshold value. If the second sensed values do not satisfy the normal condition, the processor controls the treadmill belt of the treadmill to stop running.