The invention provides a moisture-proof mounting structure of a finished mirror cabinet. The moisture-proof mounting structure comprises the mirror cabinet which is fixedly mounted on a wall surface,a water guiding mechanism is mounted on the back of the mirror cabinet and comprises a first water guiding plate which is vertically mounted, two second water guiding plates are symmetrically mountedand obliquely arranged on the inner and outer sides of the first water guiding plate respectively, and an included angle of at least 30 degrees is formed between each second water guiding plate and the first water guiding plate. Compared with the prior art, the moisture-proof mounting structure has the advantages that the purpose of preventing the mirror cabinet from getting damp can be effectively achieved, and the service life of the mirror cabinet is prolonged.