A protective cover with a heat-conductive medium of a heat sink apparatus is provided, which is used to cover and protect the heat-conductive medium placed at the bottom surface of a base of the heat sink apparatus. It includes a sheet-like board, an elastic wall, and an accommodation chamber, wherein the sheet-like board is concave and located at one side of the protective cover with the heat-conductive medium; the elastic wall is extended along the edge of the sheet-like board so as to provide a clipping force for clipping with the heat sink apparatus; and the accommodation chamber is formed by the concave portion of the sheet-like board to mask and cover the heat-conductive medium; while the sheet-like board is clipped to the heat sink apparatus through the elastic wall, such that the accommodation chamber is used to mask and cover the heat-conductive medium.