A simplified model was proposed for the interaction between multivalent species, competing with a low molecular weight competitor. This model assumed that a mixed system of multivalent species takes only two states, i.e., the free and complexed states. The simplified model was applicable to estimate the relative strength of multivalent interaction of poly(acrylic acid)-based superabsorbent polymer microparticles modified with beta-cyclodextrin and adamantane moieties.