Objective To investigate the calculation method of spray angle for soy protein spray coating dispersions ( SPCD) of the vegetable composite paper in the spraying process and the influence of spraying process parameters on atomization angle of SPSCD. Methods The spray angle of SPSCD for vegetable composite paper were calculated using MATLAB software based on the image processing method. The effect of process parameters on the spray angle produced during spraying process was also studied based on response surface methodology analysis. Results Among the single factors, the spray flow rate and pressure had a significant effect on SPSCD. The interaction of spray flow rate, air pressure and hydraulic pressure had a very significant effect on the spray angle ( 0. 0008 < 0. 05 ) . The relational model between spray angle and process parameters was built by analysis software and the optimal spraying conditions were identified. Conclusion The spray angle of SPSCD could reach 138. 2637^o , when the flow rate was 48. 04 cc / min,the air pressure was 199 Pa, and the hydraulic pressure was 151 Pa.