The invention discloses a weather-resistant water-based adhesive and a preparation method thereof. The weather-resistant water-based adhesive is prepared from deionized water, sodium acetate, disodium hydrogen phosphate dodecahydrate, a protective colloid, tartaric acid, a crosslinking agent, vinyl acetate, crosslinking monomer, oxydol, a mold preventive, a defoaming agent and a film-forming assistant. The preparation method comprises the following steps: adding the sodium acetate, disodium hydrogen phosphate dodecahydrate, protective colloid and defoaming agent into the deionized water to obtain a protective colloid solution; adding part of the vinyl acetate and crosslinking monomer into the protective colloid solution, adding all the crosslinking agent solution, and adding part of the oxydol and tartaric acid to obtain a seed emulsion; and dropwisely adding part of the vinyl acetate and oxydol into the seed emulsion, adding the rest of tartaric acid, dropwisely adding the rest of vinyl acetate and oxydol, carrying out curing reaction, adding the film-forming assistant, and adding the mold preventive to obtain the weather-resistant water-based adhesive. The weather-resistant water-based adhesive has the advantages of high bonding strength, excellent heat resistance and excellent water resistance, is convenient to use, enhances the work efficiency and lowers the cost.