The present invention relates to a retaining structure for securing at least one expansion card (such as a Peripheral Component Interconnect, PCI card) on a motherboard. The retaining structure includes a frame member and a handle. The frame member has a main body, and the main body has at least one outer fixing portion and an inner fixing portion. The main body has a top piece and a connecting piece. The connecting piece is arranged away from the outer fixing portion and connected to the inner fixing portion. The handle is connected to the connecting piece. Upon mounting of the retaining structure, the distance between the handle and a base plate of a housing is less than the distance between the top piece and the base plate of the housing. This retaining structure may be easily dismounted in restricted space internal of the housing.