In this study, the hydrolysis of pretreated sorghum stem and rice husk was investigated at various initial enzyme concentrations and substrate loadings. The slowdown in enzymatic hydrolysis of lignocellulosic materials with conversion has often been attributed to decreasing the activity of enzyme. A kinetic model was developed and expressed mathematically based on enzyme deactivation for enzymatic hydrolysis of lignocellulosic materials. The decline in activation of the adsorbed enzyme is represented by a second order reaction. The models were used to fit experimental data of sorghum stem and rice husk hydrolysis. The models basic parameters which can explain the effects observed experimentally were determined and discussed. The model performed well in predicting hydrolysis trends at experimental condition.