The invention discloses a cell protection circuit and protection method, and a wearable device. The cell protection circuit includes a switching circuit and a differential processing circuit, whereinone end of the switching circuit is connected to the ground end of a cell, and is connected to a first differential signal end of a control module; a second differential signal end of the control module is connected to the ground end of the system; and the control module receives alternating current differential signals from the ground end of the cell and the ground end of the system to calculatea phase difference of the alternating current differential signals, obtain the internal temperature of the cell by inquiring the phase difference and the cell internal temperature relationship table according to the phase difference and perform a cell protection action according to the cell internal temperature condition. The cell protection circuit has the advantages of being high in detection accuracy of the internal temperature of the cell, being timely in response, effectively protecting the cell and the system, and avoiding occurrence of events endangering security, caused by too high cell temperature.