Electrochemical redox processes of bovine heart cytochrome c were investigated by in situ UV-vis and CD spectroelectrochemistry at bare glassy carbon electrode (GCE) and single-wall carbon nanotubes (SWNTs) modified glassy carbon electrode (SWNTs/GCE) using a long optical path thin layer cell. The spectra obtained at GCE and SWNTs/GCE reflect electrode surface microstructure-dependent changes in protein conformation during redox transition. Potential-dependent conformational distribution curves of cytochrome c obtained by analysis of in situ circular dichroism (CD) spectra using singular value decomposition least square (SVDLS) method show that SWNTs can retain conformation of cytochrome c. Some parameters of the electrochemical reduction process, i.e. the product of electron transfer coefficient and number of electrons (alpha n = 0.3), apparent formal potential (E0' = 0.04 V), were obtained by double logarithmic analysis and standard heterogeneous electron transfer rate constant k0 was obtained by electrochemistry and double logarithmic analysis, respectively.