The invention relates to a self-waterproof structure for a roof. The self-waterproof structure for the roof comprises a plurality of structural base plates, a leak water collection tank and at least one draining pipe. The structural base plates are mounted on a main purline of the roof and are each of a concave-convex alternate structure formed by concave parts and convex parts. The extension direction of the concave parts and the extension direction of the convex parts are consistent with the slope direction of the roof and perpendicular to the main purline. The leak water collection tank is mounted at the intersections of the structural base plates and a draining gutter, and an opening of the leak water collection tank is lower than the bottom edges of the concave parts of the structural base plates. The draining pipes are mounted at the bottom of the leak water collection tank. Rainwater leaking from the roof enters the leak water collection tank along the concave parts of the structural base plates and then enters a rainwater recycling system through the draining pipes so as to be stored for later use. According to the self-waterproof structure for the roof, the structural base plates which are each of the concave-convex alternate structure are used as secondary waterproof structures so that the problem of rainwater leakage of the metal roof can be solved, and the structural base plates can also serve as auxiliary purline structures of the roof to achieve the waterproof function and the roof supporting function.