Abstract: One desired dopamine agents,(S) N (1 hydroxyethyl 2 pyrrolidinyl)methyl 5 amonio 2,3 dimethoxy benzamide,is synthesized in the first time.The chemical structure is confirmed by spectrum data.The radioiodination of the compound with 125 I is accomplished by an electrophilic iodination reaction using hydrogen peroxide as an oxidant and the labeled compound,(S) N (1 hydroxyethyl 2 pyrrolidinyl)methyl 5 amonio 4 125 I 2,3 dimethoxy benzamide,is obtained.The labelling yield is about 79% and the radiochemical purity is higher than 90% after extraction.The regional distribution of this complex in the brain(ratio of striatum/cerebellum is higher than 1)displays the selective localization.