An expansion interface module having protection circuit disposed on a front-side case panel and electrically connected to a main board. The expansion interface module includes a circuit board, a plurality of connectors, a protective element, and a connecting port. The connectors, protective element and the connecting port are electrically connected to the circuit board. The protective element is a semiconductor element. The protective element and the circuit board form a protection integrated circuit. One side of the main board is connected to a bus line. The bus line is inserted in the connecting port to provide electrical connection between the circuit board and the main board. Through this configuration, when an external device experiences abnormal operations, the protective element of the expansion interface module shields the resulting over current and signal spikes from entering and damaging the main board.