The charge transfer characteristic of tetraphenylporphyrin iron (III) chloride (FeP) Langmuir-Blodgett (LB) films on the surface of the ITO glass electrode was reported. When the cyclic voltammetry (CV) scanning was running, the charge transfer characteristic was controlled by the oxidation-reduction process of Fe(III)/Fe(II). The charge transfer characteristic was related to the following factors: the cross-sectional area, relative to the electrode, of FeP as the electron donor (or acceptor). The greater the cross-sectional area of the aggregation of FeP as the electron donor (or acceptor) was, the larger the number of the donated (or accepted) electrons was. The projected area of the cross-section on the ITO electrode. The greater the projected area was, the larger the number of the donated (or accepted) electrons was. The distance between the center of the electron donor (or acceptor) of FeP and the surface of ITO electrode. The smaller the distance was, the greater the rate of donating (or accepting) electrons was. The monolayer coverage, which formed because of the FeP lying on the ITO surface in the form of the monomer and aggregate, was more sensitive to detect oxygen. (C) 2013 Elsevier B. V. All rights reserved.