Abstract: A data transmitting method for communicating one of a plurality of portable devices with a host computer via a data transmitting device having a plurality of USB connector is disclosed. In one embodiment of the present invention, the method includes the following steps: firstly, a switch circuit is configured in one of the portable devices. Then, the portable device having the switch circuit is coupled with the data transmitting device. Afterward, a data transmission path between the host computer and the portable device having the switch circuit is connected by the switch circuit to transmit data between the portable device having the switch circuit and the host computer, or the data transmission path between the USB connector, which is not connecting with the portable device having the switch circuit, and the host computer is connected by the switch circuit.