The invention discloses a leakage-proof mounting method for an energy-saving auxiliary frame. The leakage-proof mounting method comprises the following steps that (1) the energy-saving auxiliary frameis mounted, specifically, the energy-saving auxiliary frame is mounted on a wall body through fixing screws, a circle of elastic gasket is mounted on the periphery of the energy-saving auxiliary frame, and the elastic gasket is mounted on the inner sides of the fixing screws; (2) inner wall plastering and inner side gap plugging are conducted, specifically, during inner wall plastering, firstly,mortar is rammed into a gap between the energy-saving auxiliary frame and the wall body, then inner wall plastering layer construction is conducted, and thus the mortar in the whole inner side pluggedgap and the mortar of an inner wall are mixed into a whole; (3) an outer side gap between the energy-saving auxiliary frame and the wall body is treated; (4) polymer mortar curing is conducted; (5) awaterproof layer is brushed, specifically, JS waterproof coating is brushed on the outer side of the wall body; and (6) outer eave construction is conducted. According to the leakage-proof mounting method, aiming at the particularity of the energy-saving auxiliary frame, the elastic gasket is mounted on the energy-saving auxiliary frame, an inner and outer double plugging method is conducted to effectively prevent the leakage problem of the energy-saving auxiliary frame, the quality of the plugged gap is ensured, and the work efficiency is improved.