A method for preparing a dispersion of conductive carbon materials is provided. The method includes dissolving a sulfonated chitosan in an aqueous solution, wherein the amount of the sulfonated chitosan of the solution is about 0.1-3 wt %. Then, a conductive carbon material is added into the solution, and the conductive carbon material in the solution is dispersed across the solution. The conductive carbon material can be carbon black or carbon nanotube.