The invention relates to a structure for fixing an expansion card. The expansion card comprises a baffle plate of which one end is provided with a bent part and a first slotted hole. The structure for fixing the expansion card comprises a flat plate, a first supporting part, a second supporting part and a fixing piece. The flat plate is positioned on one side of a machine shell and is provided with a plane facing to the inside of the machine shell. The first supporting part and the second supporting part are fixed on the plane of the flat plate respectively. The fixing piece is provided with a pressing part and at least one second slotted hole, is arranged on the first supporting part through the second slotted hole, and resists against the plane in a sliding mode while the pressing part faces to the bent part. When the fixing piece slides to a fixing position, the pressing part presses the bent part, and the baffle plate is fixed on the second supporting part through the first slotted hole and resists against the plane.