Processing conditions for a soybean-protein drink with Lactobacillus were studied. Grinding parameters of soybean and enzymatic hydrolysis of soybean were optimized in order to improve flavor and number of active Lactobacillus during storage. Soybean was boiled in 0.05% citric acid solutions for 5 minutes, and then soaked in water at 37 ℃ for 4 hours. The soaked soybean was ground to soy milk and filtered. Filtrate of soy milk was hydrolyzed by 0.5% papain at 55 ℃ for 4 hours. .Hydrolyzed milk was heated to 90 ℃ for 10 minutes to inactivate papain, and then fermented by Lactobacillus. Lactobacillus drink containing soybean peptide based on the fermented soy milk tasted good and showed non-significant beany flavor. The number of active Lactobacillus in the beverage was above 108 cfu/mL after a 30-day storage.