The kinetics of enzyme treatment of hardwood kraft pulp with Xylanase AN was investigated. The kinetics of the process was studied at different temperatures, i.e. 20, 30, 40 degrees C. Various kinetic equations, which describe the diffusional, topochemical and other heterogeneous processes were applied. The enzyme treatment process was found to follow most exactly the topochemical modified equation of Prout-Tompkins. The value of the reaction rate at various temperatures provides the calculation of the activation energy E, which was obtained as 34.1 kJ/mol. it did not depend on substrate conversion, while the pre-exponential factor decreased with the increase of the degree of substrate conversion. The data obtained from these investigations make us consider that interaction between the enzyme and xylan is carried out With one and the same energy, i.e. without changing the energy factor.