Platinum nanoparticles on polyaniline-coat multi-walled carbon nanotubes were fabricated by electrochemical method at paraffin-impregnated graphite electrode (Pt/PAN/MWCNTs). The material was characterized by various methods including field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. The electrode has been effectively applied toward formaldehyde (HCHO) sensing. A good linear response curves from 1 x 10(-9) to 1 x 10(-3) M can be obtained with a lower detection limit of 4.6 x 10(-11) M (S/N 3). The successful preparation of nanocomposites opens a new path to fabricate the promising sensor for HCHO.