NOVELTY - A platinum/carbon nanotube hybrid material is prepared by purifying a carbon nanotube using a nitric acid in a reflux condenser; filtering to separate the supernatant and the purified carbon nanotube using a cellulose nitrate membrane; washing filtered nanotube with distilled water, and vacuum drying; modifying the carbon nanotube by polymer assisting non-covalent modification using a polymer aqueous solution; stirring while subjecting to a water bath; and filtering the solution using cellulose nitrate membrane.    USE - Method of preparing platinum/carbon nanotube hybrid material (claimed) for an electrochemical sensor or fuel cell.    ADVANTAGE - The method prepares material having narrow particle size, average particle size of 3.7, and high electric catalysis capability.    DETAILED DESCRIPTION - A platinum/carbon nanotube hybrid material is prepared by:    (A) purifying a carbon nanotube using a nitric acid (3-5 mol/l) at a volume ratio of 1:1-3 in a reflux condenser for 36-48 hours;    (B) filtering to separate the supernatant and the purified carbon nanotube using a cellulose nitrate membrane having an aperture of 0.22 mu m;    (C) washing filtered nanotube with distilled water, and vacuum drying at 60 degrees C to obtain multi-wall nanotube;    (D) modifying the carbon nanotube by polymer assisting non-covalent modification using a polymer aqueous solution having a concentration of 1-10% at a frequency of 100 Hz for 6-12 hours;    (E) stirring while subjecting to a water bath controlled at 30-70 degrees C for 36-72 hours to obtain uniformly dispersed carbon nanotube water solution;    (F) filtering the solution with cellulose nitrate membrane having an aperture of 0.22 mu m, washing with distilled water, filtering, and vacuum drying at 60 degrees C to obtain polymer non-covalent modified carbon nanotube;    (G) reducing the platinum nanoparticle on the surface of the carbon nanotube using a nitric acid at a volume ratio of 1:6-8;    (H) mixing polymer non-covalent modified carbon nanotube and distilled water, and subjecting to ultrasonic processing for 0.5-2 hours;    (I) adding platinum precursor, and subjecting to ultrasonic processing for 0.5-2 hours;    (J) adding reducer, and reacting in a reflux condenser controlled at 89-120 degrees C for 0.5-1.5 hours; and    (K) subjecting to centrifuge, filtering the solution, washing the nanotube, and vacuum drying.    The polymer aqueous solution and nitric acid has a volume ratio of 1:5-8. The polymer is cation type polyelectrolyte polyethyleneimine. The platinum precursor and polymer non-covalent modified carbon nanotube has a weight ratio of 0.01-4.96:1. The reducer and platinum precursor has a weight ratio of 89-180:1. The platinum precursor is potassium tetrachloroplatinite. The reducer is formic acid.