The work aims to achieve wide coating on the premise of ensuring the uniformity of spray atomization characterization and improve the efficiency of coating, in order to get uniform and consistent coating of soybean protein. The Sauter mean diameter of the spraying and atomizing field of soybean protein liquid was measured with a particle size meter under different interference degrees, and the particle size data were processed by Spraylink software, and the particle size data were obtained and compared. With the increase of hydraulic pressure, the SMD of the double-gun spraying and atomizing field increased first and then stabilized, and decreased first and then stabilized with the increase of air pressure. When the hydraulic pressure was 0.08 MPa and 0.16 MPa, SMD did not change with the change of the deflection degree. While when the hydraulic pressure was 0.24 MPa, SMD increased with the increase of the deflection degree. The radial SMD of the double-gun spraying and atomizing field decreased slowly from the center to the edge, and the diameters of the two axial points in the interference region were basically equal. When the hydraulic pressure is 0.08 MPa, the air pressure is 0.24 MPa. When the deflection angle is 0°, SMD is relatively small. The research in this work lays a theoretical foundation for the realization of wide coating.