The invention provides a wearable device anti-theft system and a method thereof. The wearable device anti-theft system comprises a wearable device and a portable electronic device; the wearable deviceis provided with a first wireless module and a first processing module; the portable electronic device is provided with a second wireless module, a second processing module, a positioning module or adynamic sensing module, wherein the second wireless module is used for establishing a wireless connection with the first wireless module, and the second processing module is used for detecting the received signal strength indication of the wireless connection; and if the received signal strength indication is smaller than a preset signal strength value, the positioning module or the dynamic sensing module is activated to calculate the moving distance of the portable electronic device, and whether a warning mode is activated is judged according to the moving distance.