The present invention relates to a wireless computer peripheral device that comprises a first power detecting unit with a set first threshold value, coupled to the first power and; and a second power detecting unit with a set second threshold value, coupled to the first power, second power and the first power detecting unit; thereby, the power energy supplied from the second power will be cut off and the power energy supplied from the first power will be provided to the wireless computer peripheral device for using when the power energy stored in the first power is higher than the power energy stored in the second power; and the power energy supplied from the first power will be cut off and the power energy supplied from the second power will be provided to the wireless computer peripheral device for using when the power energy stored in the first power is lower than or equal to the power energy stored in the second power. Furthermore, the present invention also provides a power supplying method for wireless computer peripheral device.