The work aims to study the change law of spray field particle size distribution of soybean protein solution, to provide experimental data for choosing a suitable vegetable paper coating surface, which can get vegetable paper composite film of good quality. The spray atomization field of soybean protein was grid-enabled. The particle sizes and particle size ratio distributions of each area were respectively measured by the particle size analyzer. The axial distance of the atomization field was from about 95 μm at H=10 cm, to about 85 μm at H=15 cm, to about 65 μm at H=20 cm, and then to about 45 μm at H=30 cm. The maximum particle size ratio was gradually decreased, and the radial distance of the atomization field was from 40~50 μm at L=4 cm, to 35~40 μm at L=8 cm, to 35~40 μm at L=12 cm, and then to 30~35 μm at L=16 cm. The maximum particle size ratio was gradually reduced; under the same spray pressure and spray hydraulic pressure, as the axial distance increased, the particle size distribution range of the soybean protein solution droplets decreased, and the ratio of large-particle size soybean protein solution droplets was gradually decreased. The particle size distribution approached the direction of the small particle size, and the particle size distribution curve of the soybean protein solution droplets became steeper and steeper. When the spray pressure and the spray hydraulic pressure were constant, only the viscosity of the soybean protein solution was changed. At the same spray field position, as the viscosity of the soybean protein solution decreased, the particle size distribution approached the direction of small particle size, and the proportion of the small particle size soybean protein solution droplets was gradually decreased. The higher the spray pressure, the smaller the viscosity of the soybean protein solution, and the better the atomization effect. The spray hydraulic pressure has little effect on the atomization effect. The particle size distribution of the soybean protein solution spray field droplets gradually increases with increase of the spray penetration distance and the proportion of the small particle size droplets, and the particle size distribution curve develops toward the small particle size. At the same time, as the radial distances of the vertical axis and spray axis increase, the percentage of small particle size droplets also increases, and the particle size distribution curve develops toward the small particle size.