This research was to describe the enzymolysis process of garlic powder which was pretreated by single frequency countercurrent ultrasound. The kinetic constants for ultrasonic pretreated and traditional enzymolysis have been determined. Results showed the value of Km in ultrasonic pretreated enzymolysis decreased by 12.7% over the traditional enzymolysis, which indicates a fast reaction speed induced by ultrasound pretreatment. Degrees of hydrolysis (DH) in the enzymolysis of garlic powder were determined and kinetics of the reaction was considered in detail in relation to substrate concentration, enzyme concentration, reaction time and DH. Our results suggested a general kinetic equation for the enzymolysis model of ultrasonic pretreated garlic powder. For the model system, the calculated values agree well with the experimental data with average relative error of 4.42%. The proposed kinetic equation can be used to model the bio-reaction process of protein enzymatic hydrolysis and optimize the operation parameters for bioreactor design, (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.