Using direct polymer reaction of poly(styrene-co-maleic anhydride) (SMA), a synthesis of copolymer of styrene and N-aryl succinimide (SMI) has been investigated. SMI copolymers were synthesized from SMA copolymers by a concerted two-step reaction, which consisted of the condensation reaction (step 1) of SMA with aromatic amine to prepare a precursor, succinamic acid, for imide formation and the cyclodehydration reaction (step 2) of succinamic acid. In this article, the application of Searle＇s preparation method of N-aryl or N-alkyl maleimide to the direct polymer reaction for SMI was attempted. Compared with synthesis of monomeric imides, the imide formation in polymeric condition appeared to be a little more sensitive to the reaction condition. The optimum condition for maximum conversion was examined in terms of time, temperature, and the amount of reactants.