Although the synthesis of polyester is an important branch of interracial polycon-densation，there were only few articles dealing with the reaction behaviours and no con-vincing and decisive conclusions regarding the reaction machanism of interfacial poly-esterification have yet been reached．A systematic study has been made on the influence of various factors (catalysts，duration of reaction，temp．，cone．of reactants，nature of solvent，amount of NaOH used，etc.) upon the interfacial polyesterification of bisphenol-A with phosgen．It has been found that the amount of alkali used in the process was the main factor influencing the molecular weight of the polycarbonate obtained．As one might have expected the effect of molar ratio of initial reactant (phosgen／ bisphenol) on the molecular weight was less important than that in the conventional melt polycondensation．The conc．of bisphenol-A solution had no prominant effect upon molecular weight， while increasing of concentration of phosgen solution favored the growth of molecular weight．Quaternary ammonium salts did asist the polymerization，and in the absence of which，the highest molecular weight was not readily obtained．A major difference between interfacial polyesterification and polyamidation was that in the former case much longer reaction time was required for obtaining high mole- cular weight polymer despite of the presence of quaternary ammonium salt as catalyst．Propor choice of organic solvent was one of the necessary condition for the attain-ment of optimum results．Studies were also made of the function of water phase for interfacial polyesterifica-tion．It has been shown that the quantity of bisphenol reacted with acid chloride varies with the molar ratio of reactants and the amount of alkali used．Regulated transfer of bisphenol across the interface during the course of polyesterification was not the neces-sary condition for preparing polymers with satisfactory molecular weight．According tO the experimental results，the authers proposed a reaction machanism for interfacial polyesterification．