A theoretical model for electroenzymatic process of a modified microcylinder electrode in which polyphenol oxidase occurs for all values of the concentration of catechol and o-quinone is presented. The model is based on system of reaction-diffusion equations containing a non-linear term related to Michaelis-Menten kinetics of the enzymatic reaction. In this paper, we implement a new analytical technique (He's variational iteration method) is used to solve the system of non-linear differential equations that describe the diffusion coupled with a Michaelis-Menten kinetics law. Herein, we report the closed form of an analytical expressions pertaining to the concentration of catechol and o-quinone and corresponding current in terms of dimensionless reaction-diffusion parameters gamma(E), gamma(S), alpha, r(1)/r(0)(=alpha(1)), enzyme kinetics (chi r(0)) and Michaelis-Menten constant (K-M). A simple relation between the concentration of catechol and o-quinone also obtained. A good agreement with available limiting case results is noticed. The obtained results are valid for the whole solution domain. (C) 2011 Elsevier B.V. All rights reserved.