A multi-walled carbon nanotubes (MWCNTs) modified carbon ionic liquid electrode (CILE) was fabricated and used to investigate the electrochemical behavior of guanosine. CILE was prepared by mixing hydrophilic ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4), graphite powder and liquid paraffin together. The fabricated MWCNTs/CILE showed great electrocatalytic ability to the oxidation of guanosine and an irreversible oxidation peak appeared at 1.067 V (vs. SCE) with improved peak current. The electrochemical behavior of guanosine on the MWCNTs/CILE was carefully studied by cyclic voltammetry and the electrochemical parameters such as the charge transfer coefficient (a) and the electrode reaction standard rate constant (k(s)) were calculated with the result as 0.66 and 2.94 x 10(-4) s(-1), respectively. By using differential pulse voltammetry (DPV) as the detection method, a linear relationship was obtained between the oxidation peak current and the guanosine concentration in the range from 1.0 x 10(-7) to 4.0 x 10(-5) mol/L with the detection limit as 7.8 x 10(-8) mol/L (3 sigma). The common coexisting substances showed no interferences to the guanosine detection and the modified electrode showed good ability to distinguish the electrochemical response of guanosine and adenosine. (C) 2009 Elsevier Ltd. All rights reserved.