Abstract: To obtain the preparation conditions and explore the physico-chemical properties of coating-agent for controlled-fertilizer, the single factor tests of the composite ratio of film-forming materials, the amount of film-forming materials, plasticizer, emulsifier and pigment were made with two resins as the film-forming materials, and the optimal preparation conditions of coating-agent for controlled-fertilizer were determined by orthogonal test L9(34). The physico-chemical properties of the pH, viscosity, film-forming time, film-forming properties, water solubility of coated film, coating uniformity, coating-off rate were measured. The results showed that, the optimal preparation conditions were as follows: the composite ratio (JZ:BZ) was 1:1.5, amount of film-forming materials was 12%, plasticizer was 0.8%, emulsifier was 1.0%, pigment was 0.08% and solvent was 86.12%. Test results of physico-chemical properties showed that, the pH was 5.21, viscosity was 21.1 MPa/s, the film was good and indissolvable in water, the film-forming time was 6 min, coating uniformity was 95%, coating-off rate was less than 8%, which indicated that the coating-agent for controlled-fertilizer had good physico-chemical properties.