Abstract: Polyamine polyethyleneimine (PEI) was grafted onto micronsized silica gel particles in the manner of “grafting to” with γchloropropyltrimethoxysilane as intermedium, forming the grafted particles PEISiO2. Subsequently, the nucleophilic substitution reaction between chloroactic acid and the amino groups of PEISiO2 was performed, resulting in the bonding of imidoacetic acid (IAA) groups onto grafted particles PEISiO2 and obtaining the composite chelating particles IAAPEISiO2 with polydentate ligand. The preparation process of IAAPEISiO2 particles was researched mainly, and the chelating adsorption character of the composite chelationg particles IAAPEISiO2 was preliminarily examined for heavy metal ion and rare earth ion. Results showed that the mechanism of this nucleophilic substitution reaction between chloroactic acid (CAA) and the amino groups of PEISiO2 is SN2. The higher reaction temperature and excessive acid acceptor NaHCO3 could accelerate the hydrolysis reaction of chloroactic acid, and restrained the substitution reaction, leading to the lower bonding ratio of IAA group. The fitting temperature was 60 ℃, and the appropriate amount of acid acceptor NaHCO3 was used in the reaction system, the molar ratio NaHCO3 to CAA was made to be equal to 1∶1. Compared with the grafted particles PEISiO2, the adsorption capacity of the chelating particles IAAPEISiO2 towards Cu2+ and Eu3+enhanced remarkably, displaying the strong chelating adsorption character.