The invention relates to a metal proofing system, particularly relates to a connection node of a metal proofing system for a solar photovoltaic building and a mounting method, and belongs to the field of steel structures. An insulating layer is arranged on a secondary purline of a roof; a metal proofing plate is arranged on the insulating layer; the metal proofing plate is fixed through a spliced supporting strip; a clamping piece is arranged on the lateral wall of the lower end of a clamping base; the clamping piece and the clamping base form a clamping opening and clamp a spliced position; a skeleton is fixed above the clamping base; a guide groove purline is arranged on the skeleton; and a solar panel component is arranged on the guide groove purline. The connection node of the metal proofing system for the solar photovoltaic building and the mounting method are simple in structure and strong in supporting property, fully utilize solar energy resources and have wind resistance.