Hybrid nanocomposites containing Pt nanoparticles (nano-Pt)and poly(3-methylthiophene)(P3MT)nanorods at glassy carbon surfaces have been successfully prepared by use of an in situ cyclic voltammetry (CV)method. Field emission scanning electron microscope (FE-SEM), electrochemical impedance spectroscopy (EIS)and cyclic voltagrams were used to characterize the properties of these nanocomposites. SEM images showed that nano-Pt were located on the surface of P3MT nanorods and that they formed a three-dimensional (3D)porous nanostructure. EIS and CV results demonstrated that these hybrid nanocomposites had good conductivities, and could accelerate the electron-transfer rates of redox ions. From the results of electrochemical oxidation of methanol and nitrite, we observed that this nanocomposite-modified electrode exhibited excellent electrocatalytic activity, which might be useful in biosensors and/or fuel cells.