Aminolysis reaction between polyarylsulfones and organic amines was investigated. A bimolecular nucleophilic substitution mechanism was proposed. The nucleophilic reagent attacks the aryl ether bond carbon on the aryl ring carrying substituents with strong electron-attracting character. 1 H NMR and 1 H– 1 H COSY NMR spectroscopies were adopted to characterize the chemical structure of the products, the terminal groups especially. The effect of polyarylsulfone structure on the reactivity was studied by comparing the reaction rates. The aminolysis kinetics of polyethersulfone with ethylenediamine at different temperature and reagent concentration was studied in detail. The molar mass of the aminolyzed product was determined by GPC and theoretical deduction, and they showed great consistency.