A chelating vinyl monomer, glycidyl methacrylate (GMA)-iminodiacetic acid (IDA), was formed by the reaction between GMA and IDA. Three polymeric chelating agents, PGMA-IDA, PGMA-IDA-co-methyl acrylate (MA), and PGMA-IDA-co-acrylamide (AAm), were also synthesized. Acid dissociation constants and stability constants of these chelating agents with Ni(II), Zn(II), and Co(II) were determined by means of potentiometric titration and ultraviolet-visible spectrophotometry, respectively. The values of K-a1 and K-a2 of all the polymeric chelating agents were smaller than those of GMA-IDA. The stability constants of all the polymeric chelating agents were larger than those of GMA-IDA. Increasing the MA content within PGMA-IDA-co-MA affected the stability constant only slightly. A proper molar ratio of AAm in PGMA-IDA-co-AAm, stability constants was 30-60 times greater than that of GMA-IDA. However, as the molar content of AAm increased, the stability constant of PGMA-IDA-co-AAm decreased. The results obtained in the polymer system are explained in terms of the polymer's stereo and entanglement structure, the neighboring effect, and the hydrophobic/hydrophilic nature of MA or AAm.