Surface coating method of ammonium salts

The invention relates to a surface coating method of ammonium salts. The method comprises emulsifying a mixture of a disperse medium, an aqueous formaldehyde solution and a silicate solution through a conventional emulsification method to obtain a water in oil type emulsion or a water in oil type microemulsion, adding ammonium salt particles, which need to be coated, into the emulsion or the microemulsion, mixing the ammonium salt particles and the emulsion or the microemulsion at a normal temperature to make a surface of each one of the ammonium salt particles be coated with a uniform and dense coating layer, and treating the resulting products by separating and drying processes to make surfaces of the ammonium salt particles be coated with water-insoluble silica coating layers. Comparedwith other physical coating methods, the method provided by the invention has the characteristics of uniform and dense coating layer, no agglomeration between particles and controllability of a coating thickness, and a moisture rate of a sample coated through the method provided by the invention is far lower than moisture rates of samples coated through other methods.