Elaboration of the technical principle of a novel method (the current disturbance method) to measure the current fraction of carbon dioxide (CFCD) during electro-oxidation of methanol is the topic of this paper. In the current disturbance method, the CFCD measurement is realized through constitution of a special CO2 evolution hole that can improve the evolution behavior of CO2. The improved gas, growth of a big bubble and escape of the big evolution behavior is composed of three regular serial processes: collection of small bubbles. bubble. The regular growths and escapes of the big bubbles can bring regular disturbances to a steady current. With the disturbances as the indicator of the forming rate of CO2, the CFCD measurement is realized. The disturbance method needs no other expensive instruments and equipments but a potentiostat, and, only one potentiostatic curve is enough to obtain the current data and the fraction data. With its straightness, simplicity, rapidness and veracity, the disturbance method provides the pick of the catalyst for methanol electro-oxidation and the study of the electro-oxidation mechanism of methanol with a powerful tool. (c) 2005 Elsevier B.V. All rights reserved.