The invention provides a water-soluble adhesive and a preparation method thereof. The water-soluble adhesive is prepared mainly by natural latex, soft water, a vulcanizing agent, a vulcanization accelerator, a vulcanizing activator, a dispersant, anhydride casein, borax, a stabilizer, a wetting agent, ammonia and potassium hydroxide. In order to improve the performance of the water-soluble adhesive, carboxymethyl cellulose sodium, the wetting agent, an age inhibitor, an antifoaming agent and a mildew inhibitor also can be added; the obtained water-soluble adhesive is an environment-friendly material which is used for shoes, has the processing advantages of low energy consumption, non-toxicity, good processing property, simple operation and the like in the preparation process, strengthens self deterioration resistance, greatly prolongs the storage stabilization period of slurry, improves the intrinsic performance of the adhesive, and fundamentally realizes the demand of high adhesive strength on rubber shoes.