In order to more intuitively evaluate the spray atomization degree of soybean protein liquid, the spray situation with larger effective sector area and fewer defects was assisted to screen out, which was conducive to the study of the atomization uniformity of the spray field, in order to obtain uniform soybean protein film. After selecting appropriate thresholds, the images taken by Particle Image Velocimetry (PIV) were binarized to delimit the spraying effective area. The proportion of points in the spraying spraying effective area was calculated by using the binarization Image. The value was defined as the relative atomization degree. The variation trend of relative atomization degree was studied by changing the consistency coefficient and spraying parameters. The relative atomization degree of soybean protein liquid with low consistency was less affected by spraying parameters and remained above 90% . The relative atomization degree of soybean protein liquid spray with medium and high consistency coefficient decreased with the increase of spraying flow, and had a tendency to increase with the increase of, hydraulic pressure and air pressure, and first increased and then decreased with the increase of gas-liquid ratio. PIV image processing based on binarization can effectively assist in evaluating the uniformity of soybean protein liquid spray field.