Provided are an interface expanding method and device. It is detected whether there is a voltage input at a power supply pin of the interface, an impedance between a signal indication pin of the interface and a ground pin of the interface is detected when no voltage input is detected, and a type of a cable inserted into the interface is determined according to the detected impedance; it is detected whether there is a short circuit or an open circuit between a data signal positive pin of the interface and a data signal minus pin of the interface when the voltage input is detected, and the type of the cable inserted into the interface is determined according to the detected result; and a relevant component in the tablet computer is controlled, according to the determined type of the calle inserted into the interface, to operate correspondingly.