Functional groups modified polymeric adsorbents were designed based on semiempirical molecular orbital theory, and the newly polymeric adsorbent named FZH124 modified with 1,2,4-benzenetricarboxylic anhydride was prepared. The static adsorption and desorption characteristics for phthalimide or anthranilic acid in aqueous solution at the temperature range of 288~318K on FZH124 or NDA150 were studied to confirm the existence of chemisorption effects, which was interpreted by the approximate orbital energy level difference between adsorbent and phthalimide calculated with the semiempirical molecular orbital method PM3. The result indicates that chemisorption effects exist in the adsorption system of phthalimide in aqueous solutions with FZH124 at the proper temperature. The capacities of phthalimide adsorbed onto the polymeric adsorbents modified with 1,2,4-benzenetricarboxylic anhydride were increased greatly, and the mechanism for the adsorption was investigated further. The separation method of phthalimide from anthranilic acid solution was also designed.