NOVELTY - Producing fertilizer synergistic additive involves: processing wood powder particle with grain diameter of 1-50 microns; putting the obtained wood powder particle into a pressure container at pressure of -0.5 to -0.2 MPa, and at 450 degrees C, injecting fertilizer solution to soak the wood meal particle in fertilizer solution and drying; preparing mixed particles by processing zeolite particle, Bacillus subtilis and the prepared dried wood powder, spraying coating liquid of the mixed solution of polyaspartic acid and binder and coating granular fertilizer synergistic additive.    USE - For production of fertilizer synergistic additive (claimed) for grains.    ADVANTAGE - The method improves the fertilizer utilization rate by 40-50%, saves fertilizer using amount on the surface of the mixed particles.    DETAILED DESCRIPTION - Production of fertilizer synergistic additive involves: processing wood powder particle with grain diameter of 1-50 microns; putting the obtained wood powder particle into a pressure container at a pressure of -0.5 to -0.2 MPa, and at 450 degrees C, injecting fertilizer solution to the pressure container to soak the wood meal particle in the fertilizer solution, at for 5-10 minutes at a pressure and temperature conditions to recover the pressure of the container to soak for 2 hours; drying the obtained soaked wood powder particle; obtaining mixed particles by processing zeolite particle with grain diameter of the zeolite particle is 3, Bacillus subtilis and the obtained dried wood powder in a weight ratio of 3:0.5:8:0.7:3 to obtain mixed particles comprising a film forming chamber; spraying coating liquid (0-30 wt.%) on the obtained mixed particles in fluidized bed device, on the mixing particle surface to form the mixed film which is formed on the particle surface, where the coating temperature of the coating chamber is 445 degrees C, the pressure is adjusted to mix particulate matter to a top half of the film forming chamber in the fluidized bed, the atomization pressure is 0.2-0.5 MPa, and the coating liquid is the mixed solution of polyaspartic acid (30-50 wt.%) and binder (1-15 wt.%), exhausting the coating liquid in the mixed solution to obtain granular fertilizer synergistic additive; and coating granular fertilizer synergistic additive to obtain coated finish.