The invention provides a determination method for Cd<2+> adsorption capacity of an electrolytic graphite nanometer sol. The method is characterized by comprising the following steps: mixing a graphite nanometer sol with a Cd<2+> solution of a same volume; then carrying out digestion by using H2SO4-H2O2; diluting a digestion solution; determining the concentration of Cd<2+> in the solution by using a flame spectrophotometer; reckoning a calculation formula for Cd<2+> adsorption capacity of the graphite sol through a series of experiments; and substituting any given Cd<2+> concentration into the formula to calculate the Cd<2+> adsorption capacity of the graphite nanometer sol. The rapid determination method for Cd<2+> adsorption capacity of the graphite nanometer sol in the invention can provide technical support for treatment of Cd<2+> contamination. The method has the following advantages: since the electrolytic graphite nanometer sol is a negatively charged nanometer particle with a small size and high surface energy activity, the electrolytic graphite nanometer sol can form polymer with heavy metal ions in the solution, so the effects of adsorption and removal of heavy metals are obtained; and the method has wide application prospects in treatment of heavy metal contaminated water.