A peripheral interface chip and a data transmission method thereof are provided. The peripheral interface chip includes a switching circuit, a universal serial bus (USB) host controller, a keyboard controller and a microprocessor. The switching circuit receives a device identification transmitted from a USB device, and the device identification is used for determining whether the USB device is a keyboard device. When the USB device is the keyboard device, input data of the USB device is transmitted to a controller hub through a first USB interface, the switching circuit, the USB host controller, the microprocessor, the keyboard controller and a low pin count (LPC) interface.
