A master-slave interchangeable power supply device, a power supply method, a host with the master-slave interchangeable power supply device, and a computer-readable storage medium for use in execution of the power supply method are provided. Upon receipt of a start command, a power control module and a power supply unit of the power supply device operate in a master mode and a slave mode respectively, and then the power supply device provides a working power to a master device to effect related configuration of the power supply device, so as to allow the power control module to switch to the slave mode and allow the working power to be provided to the master device. Therefore, given compliance with a specification of a communication bus, the power control module and the power supply unit, which function as peripheral devices, can perform a communicative function.