The invention relates to a polymer metal salt, a preparation method of the polymer metal salt and application of the polymer metal salt in preparing anti-fouling paint. The preparation method comprises the step of: dropwise adding inorganic acid salt aqueous solution of calcium, magnesium, copper or zinc to aqueous solution of alkali metal salt of carboxymethyl chitosan carboxylic acid, carboxymethyl cellulose carboxylic acid or carboxylic acid and micromolecular organic acid alkali metal salt to carry out precipitation reaction so as to obtain the polymer metal salt. The low-toxicity or no-toxicity micromolecular organic acid released during the hydrolysis of the polymer metal salt in seawater can effectively prevent the adhesion of fouling organisms; and the residual carboxymethyl chitosan or carboxymethyl cellulose or alginic acid polymer residue after hydrolysis still has certain anti-fouling performance, and the hydrophilic carboxylate on the polymer residue is dissolved in seawater after being increased to certain quantity, so that the coating is endowed with polishing property. The polymer metal salt has the environment-friendly characteristic; and the environment-friendly type anti-fouling paint prepared by the polymer metal salt also has better anti-fouling effect.