The invention provides preparation methods of water-based slurry and a water-based carbon stable liquid and a use of the water-based carbon stable liquid. The preparation methods comprise the steps: adding a carbon material subjected to full carbonization treatment into ultrapure water, successively carrying out ball milling, sand grinding, ultrasonic treatment, homogenization and other treatment to obtain the water-based slurry; and then diluting the water-based slurry until the carbon concentration is 5 ppm-0.5%, and thus obtaining the water-based carbon stable liquid. The preparation methods of the water-based slurry and the water-based carbon stable liquid are carbon material water-based dispersion methods developed through a lot of researches; in the water-based carbon stable liquid obtained through the preparation method, the concentration of carbon in the stable liquid can reach 5 ppm-0.5%, and a basis is provided for wide application of the water-based carbon stable liquid; the water-based carbon stable liquid prepared by the method provided by the invention can be applied in biomedicine, battery diaphragm manufacturing, stealth coating manufacturing, daily chemical product manufacturing and various other fields.