Abstract: Based on the preparation technology of soybean milk powder by wet processing,a combination of ultrasound and enzymatic hydrolysis was adopted to improve the solubility of soybean milk powder. On the basis of single factor experiment,technological parameters for preparation of soybean milk powder with higher solubility were determined by response surface methodology to optimize the combination parameters of ultrasound and enzymatic hydrolysis as follows:350 W ultrasonic power treated for 23 min,then enzymatic hydrolyzed at p H8.6,57 ℃,for 1.7 h. Under this optimal processing condition,the protein dispersibility index reached 88.79%,which was nearly 10 percent higher than that of the soybean milk powder without the combined treatment of ultrasound and enzymatic hydrolysis. The solubility of soybean milk powder had increased significantly.