In this work, electropolymerization of carboxylated conducting polymer/CNTs composites have been studied for construction of surface plasmon resonance immunosensor. The electrochemical experiment was performed in 1.0 M tetrabutylammonium hexafluorophosphate (TBAPF6) in acetonitrile containing 10 mM monomers, thianaphthene-2-carboxylic acid and benzothiophene-2-propanoic acid, and CNTs in acetonitrile at scan rate of 20 mV/s using platinum wire as counter electrode and Ag/Ag+ as reference electrode with potential range of 0 V to 1.2 V for 5 cycles. The gold and ITO-coated glass substrates were used as working electrode where the electropolymerization was occurred. The obtained films were characterized by UV-vis absorption spectroscopy, atomic force microscopy and in situ electrochemical-surface plasmon resonance spectroscopy. Further studies about immobilization process are under investigating for this immunosensor system. © 2011 The Institute of Electrical Engineers, Japan.