A USB charging circuit includes a mating hub module including a USB input port for the connection of an external computer and a USB main hub control circuit electrically connected to the USB input port, a power supply module including a power supply device and a synchronization/charge mode switching circuit for detecting the power signal output of the USB input port and outputting a corresponding mode judgment signal, and one or multiple output control units each including a USB charging control circuit electrically connected to the USB main hub control circuit, the power supply device and the synchronization/charge mode switching circuit to receive the outputted data signal, power supply and mode judgment signal and a USB output port for receiving the outputted data signal and power supply from the USB charging control circuit so that connected portable electronic devices can be charged or receive data synchronously.