The electrochemical degradation of methyl orange (MO) dye over the electrospun activated carbon fiber (ACF) webs modified with carbon nanotubes (CNTs) (e-CNT/ACF) has been studied. The CNTs in the web-like e-CNT/ACF composites help to improve the pore distribution and conductivity of the concerned composites. With e-CNT/ACF webs as electrodes, about 90% of the MO can be degraded in 60 min, which is much higher than the commercial woven ACF under the similar conditions. The effects of the electrolysis potential, pH and electrolyte concentration on the MO degradation have been addressed in detail. The results show that the MO degradation efficiency over the e-CNT/ACF webs is related linearly to the potential and the electrolyte concentration, while for the pH, it goes through an optimum value of 3.0. (C) 2014 Elsevier B.V. All rights reserved.