The aim of this work is to study the development of the macroscopic non-uniformity of the electron density of high pressure discharge for excimer lasers and eventually its propagation because of the medium kinetics phenomena. This study is executed using a transverse mono-dimensional model, in which the plasma is represented by a set of resistances in parallel. The time variations of the electron density in each plasma element are obtained by solving a set of ordinary differential equations describing the plasma kinetics and external circuit. The use of the present model allows a good comprehension of the halogen depletion phenomena, which is the principal cause of laser operation premature termination and allows a simple study of a large-scale non-uniformity in preionization density and its effects on plasma electrical and chemical properties. The results obtained indicate clearly that about 50% of halogen is consumed at the end of the pulse.