An interface expanding device for a tablet computer, which is built in the tablet computer, the device comprising an interface, a voltage detection unit, an impedance detection unit, a charging detection unit and a central processing unit, wherein the interface is configured to allow a cable to be inserted thereinto; wherein the voltage detection unit is configured to detect whether there is a voltage input at a power supply, VBUS, pin of the interface, notifying the impedance detection unit when no voltage input is detected, and notifying the charging detection unit when the voltage input is detected; wherein the charging detection unit is configured to, after receiving the notification from the voltage detection unit, detect whether there is a short circuit or an open circuit between a data signal positive, DP, pin of the interface and a data signal minus, DM, pin of the interface; and wherein the central processing unit is configured to determine a type of a cable inserted into the interface, and control, according to the determined type of the cable inserted into the interface, a relevant component in the tablet computer to operate correspondingly, the impedance detection unit is configured to, after receiving the notification from the voltage detection unit, detect an impedance between a signal indication, ID, pin of the interface and a ground, GND, pin of the interface, the central processing unit is configured to determine the type of cable inserted into the interface according to the impedance detected by the impedance detection unit or a detection result from the charging detection unit, and the central processing unit is further configured to: when the impedance detected by the impedance detection unit is 0 ohm, determine that the cable inserted into the interface is an A-type Universal Serial Bus, USB, cable through querying the correspondences between preset impedances and cable types; when the impedance detected by the impedance detection unit is larger than or equal to 34.6 kilo-ohms and smaller than or equal to 36.8 kilo-ohms, determine that the cable inserted into the interface is a video cable through querying the correspondences between preset impedances and cable types; when the impedance detected by the impedance detection unit is larger than or equal to 64.6 kilo-ohms and smaller than or equal to 71.4 kilo-ohms, determine that the cable inserted into the interface is an audio cable through querying the correspondences between preset impedances and cable types; when the impedance detected by the impedance detection unit is larger than or equal to 198 kilo-ohms and smaller than or equal to 202 kilo-ohms, determine that the cable inserted into the interface is a cable for vehicular equipments through querying the correspondences between preset impedances and cable types; and when the impedance detected by the impedance detection unit is infinite, determine that the cable inserted into the interface is a B-type USB cable through querying the correspondences between preset impedances and cable types. when the impedance detected by the impedance detection unit is 0 ohm, determine that the cable inserted into the interface is an A-type Universal Serial Bus, USB, cable through querying the correspondences between preset impedances and cable types; when the impedance detected by the impedance detection unit is larger than or equal to 34.6 kilo-ohms and smaller than or equal to 36.8 kilo-ohms, determine that the cable inserted into the interface is a video cable through querying the correspondences between preset impedances and cable types; when the impedance detected by the impedance detection unit is larger than or equal to 64.6 kilo-ohms and smaller than or equal to 71.4 kilo-ohms, determine that the cable inserted into the interface is an audio cable through querying the correspondences between preset impedances and cable types; when the impedance detected by the impedance detection unit is larger than or equal to 198 kilo-ohms and smaller than or equal to 202 kilo-ohms, determine that the cable inserted into the interface is a cable for vehicular equipments through querying the correspondences between preset impedances and cable types; and when the impedance detected by the impedance detection unit is infinite, determine that the cable inserted into the interface is a B-type USB cable through querying the correspondences between preset impedances and cable types.