The work aims to research the average density of soybean protein spraying on the parchment paper and the influence of spraying parameters and belt velocity on the average spraying density. Firstly, the spraying image was collected by the camera and then the area ratio of soybean protein solution was processed and calculated by software Matlab. The larger the area ratio was, the better the spraying effect of soy protein was. The effect of spraying parameters and belt velocity on the average spraying density was also studied based on response surface analysis. When hydraulic pressure was 159 Pa, air pressure was 180 Pa and belt velocity was 11.93 mm/s, the area ratio of soybean protein solution could be up to 79.9079%, which was the best. Among the single factors, the hydraulic pressure and belt velocity has a significant effect on the average spraying density. The relational model between the area ratio of soybean protein solution and the spraying parameters & belt velocity is built through analysis software, and the optimal spraying conditions are identified.