The invention discloses a method for bottom sealing leaking stoppage and waterproof and drainage construction of a rock riverbed steel cofferdam. The method includes a first step of cofferdam construction, a second step of placing down steel pile casing, a third step of cofferdam bottom sealing, a fourth step of construction of bored piles, a fifth step of concrete bottom sealing layer leaking stoppage construction, a sixth step of water drawing in the cofferdam and steel pile casing removal and a seventh step of waterproof and drainage construction: a waterproof and drainage structure is constructed in the steel cofferdam. The waterproof and drainage structure includes a drainage structure, a permeable layer laid on a concrete bottom sealing layer, a bottom water-resisting layer laid on the permeable layer and a side water-resisting layer laid on the inner side wall of the bottom of the steel cofferdam. An integrated water-resisting layer composed of the bottom water-resisting layer and the side water-resisting layer is adopted to isolate a bearing platform from a bottom sealing concrete layer and the inner side wall of the steel cofferdam, seepage water in the steel cofferdam canbe effectively prevented from entering the bearing platform, and the permeable layer is arranged between the bottom water-resisting layer and the bottom sealing concrete layer, to quickly discharge the seepage water on the outer side of the integrated water-resisting layer into peripheral drainage ditches, so that the waterproof and drainage problem of the steel cofferdam can be effectively solved.