Abstract: In order to optimize the pulping process of domestic soybean milk machine, response surface methodology was applied in the experiment. Using soybean as raw material in wet-milling mode, we investigated the influence of three factors(soaking time, soaking temperature, soybean/water ratio)on the rate of water absorption, pulping rate, soluble solids content and soluble protein content in the process based on the results of single-factor experiment. According to the Box-Behnken center-united experimental design principles, three factors and three levels was adopted and mathematical models of soluble protein content were set up to obtain the optimum pulping process of domestic soybean milk machine. The optimum condition was determined as follows:soaking time for 12 h, soaking temperature at 25℃, and soybean/water ratio of 1:9 g/mL. Under the optimum condition, the protein content of soluble soybean milk was significantly improved and reached 14.36% which was well matched with the predicted value(14.52%). The optimized process conditions of domestic soybean milk machine was reasonable and feasible, as the protein content of soluble soybean milk obviously increased. Therefore, the experiment provided a certain data support for the establishment of the quality evaluation standard of soybean milk produced by the domestic soybean milk machine.