The invention provides a roof periphery waterproofing system, and relates to the technical field of grid-type steel combination support structure construction. The system comprises a main beam which is arranged on one side of a parapet, wherein a secondary beam, a roofing steel plate, a waterproof layer, a leveling layer, an insulating layer, an isolation layer, a protective layer and a decorative layer are arranged on the main beam in sequence. The system is characterized in that a section of upward folded steel plate is continuously connected to the end part of the roofing steel plate closeto the parapet, and the upper end of the folded steel plate is higher than the decorative layer; a vertical insulating waterproofing layer is arranged between the parapet and the folded steel plate section; a cement mortar raised line is arranged between the end part of the decorative layer and the folded steel plate section; a galvanized iron sheet is fixed on the parapet, and the lower end of the galvanized iron sheet is coated on the cement mortar raised line; and when water of the parapet flows down, the water can flow to the decorative layer on the roof along the outer surface of the galvanized iron sheet, rather than flowing into the gap between the roofing layer and the parapet. The roof periphery waterproofing system is convenient to construct, so that the waterproofing performance of the roof can be effectively improved.