Di-2,2,2-trichloroethyl cis-epoxysuccinate, di-2-cyanoethyl cis-epoxysuccinate, and di-2-methoxyethyl cis-epoxysuccinate were synthesized, and the substituent effect of the epoxysuccinates on the polycondensation with diamine was studied. The order of reactivities of the epoxysuccinates with m-xylylenediamine was as follows: di-trichloroethyl ester much greater than di-cyanoethyl ester > di-methoxyethyl ester, such was also confirmed by the model reaction of the epoxysuccinate with benzylamine. H-1 NMR and IR spectroscopic study and ab initio calculation also well explained the reactivity order.