Poly(vinyl alcohol) phosphorylate was prepared and its complex with dicyandiamide-formaldehyde resin was used for adsorption and separation of Sm3+, Nd3+, Gd3+, Ho3+, and Er3+ ions. The factors that affect the adsorption and separation of these ions on the polyacid-polybase complex, such as the acidity of the sample solution, adsorption capacity, and conditions of desorption, were investigated by means of spectrophotometry and inductively coupled plasma optical emission spectrometry. IR spectrometry and X-ray photoelectric spectrometry were used to study the adsorption mechanism, and the probably coordination structure was given.