The interface behavior and biocatalytic activity of superoxide dismutase (SOD) were studied at carbon nanotube (CNT) surface with cyclic voltammetry (CV). The results show that SOD participates in a rapid exchange with CNT and the process is a single-electron-single-proton process. The electron-transfer coefficient was calculated to be 0.52, the electron-transfer rate constant was 1.4s(-1) and the average surface coverage was measured to be 6.93 x 10(-11)+/-4.2 x 10(-12) mol cm(-2). The bioactive measurements show that SOD keeps its bioactivity at the CNT surface. SOD's remarkable ability to catalyze the dismutation of the superoxide anion (O (2)(-)) has been demonstrated.