In order to prepare the controlled-release type herbicides of 2,4-dichlorophenoxyacetic acid (2,4-D) and its analogues, 2,4,5-trichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, and 2-(2,4-dichlorophenoxy) propionic acid, the herbicidal monomers were synthesized by reacting chloromethylstyrene with the sodium salts of 2,4-D and its analogues in chlorobenzene in the presence of triethylamine at 90℃. The herbicial polymers were prepared by radically copolymerizing acryamide as hydrophilic monomer with th herbicidal monomers in dimethylformamide at 70℃. Then, the amounts of the herbicides released through the hydrolysis of the copolymers were measured. As a result, the release rates of the herbicides from the copolymers with about 10 mol% of the hervicidal monomers were controlled more effectively with respect to the herbicies than those of the hervicides from the copolymers with about 5 mol% of the herbicidal monomers. This result could be explained in terms of the contents and the hydrophobicity of th herbicidal monomers in the copolymers.