The invention relates to the technical field of chemical analysis, in particular to a method for measuring the cation degree of amphoteric ion sulfonated phenolic resin. The method comprises steps asfollows: firstly, the adsorption quantity m(adsorption) of every 0.5 g of pure amphoteric ion sulfonated phenolic resin in diatomite is measured, then the adsorption quantity m(adsorption) is substituted into a formula as follows: A=863.87m(adsorption)-24.54, and the cation degree A of the amphoteric ion sulfonated phenolic resin is calculated. On the basis that cationic quaternary ammonium groupson molecular chains of the amphoteric ion sulfonated phenolic resin have good adsorption performance, adsorption mass is calculated according to mass change of a to-be-tested sample before and afteradsorption by utilizing the diatomite as a standard adsorbing medium; according to the cation degree measuring method based on an adsorption weighing method, the influence of anions on the measuring process and a measuring result in the prior art is avoided, accuracy of a detection result is improved, furthermore, the method has wide applicability and higher operability, the requirement for instruments and equipment is low, and the method can be popularized and applied in conventional detection laboratories.