The invention provides a method for dispersing a carbon nano-tube by degradable biological molecules and further preparing a carbon nano-tube film having low sheet resistance or having low sheet resistance and high transmittance in high production efficiency. The method is characterized in that the selected biological molecules are amphiphilic molecules with both lipophilic structure, such as long carbon chain frames and the like and hydrophilic groups, such as SO3-, PO4-, COO-, -OH and the like, thus having strong dispersing ability towards the carbon nano-tube. The suspension of the carbon nano-tube which is dispersed by the biological molecules has high concentration, small control size and good stability, and the required amount of the dispersant is far less than that of the traditional dispersant, such as SDS, SDBS and the like, thus reducing the contact resistance greatly introduced by the dispersant, and therefore, the prepared carbon nano-tube film has excellent electrical conductivity. The biological molecules basically have no absorption in a visible region, thus having little influence on the transmittance of the film. Moreover, the biological molecules are degradable and are easy to be removed from the film, thus providing an effective approach to further improve the electrical conductivity of the film.