A charging system based on a master-slave relationship includes a master charging device coupled with a target device, and at least one slave charging device electrically connected with the master charging device. An edge slave charging device among the at least one slave charging device is coupled with a power source. The master charging device determines a power-output distribution of the master charging device and the at least one slave charging device, and notifies the at least one slave charging device of the power-output distribution. The at least one slave charging device provides a supplementary power to the master charging device according to the power-output distribution. The master charging device further provides a specific power for the target device based on the supplementary power, so as to charge the target device in cooperation with the at least one slave charging device.