A wearable power supply includes a strap to be worn on a user's wrist, arm, waist, leg or head; a flexible secondary battery carried by the strap; and a connector slot disposed on the strap and electrically connected to the flexible secondary battery, wherein the flexible secondary battery is capable of supplying current to a mobile device via a connecting wire connected between the connector slot and the mobile device, and is recharged from an external power supply connected to the connector slot. When the wearable power supply takes the form of a wristband, it can be used as a carrier of a hand worn mobile device, such as a smart watch or a smart bracelet, to provide a longer operating range.