The formation of hyperbranched polymers (HBPs) generated by the stepwise polymerization of AB(2) monomers with the addition of trifunctional core monomers in a continuous-stirred tank reactor, CSTR, was investigated by a kinetic model. The dependency of the degree of polymerization (DP), the degree of branching (DB), and conversion on the Damkohler number (Da) were calculated by a generating function method. When using the polymerization system without the core monomers, the process could be halted due to the production of larger molecules at the conversion of group A, alpha(A), of approximately 0.44. The addition of core monomers with high reactivity in the CSTR could retard the growth of polymers. Consequently, the reduced weight-average DP and DB could reach 1000 and 0.51, respectively, at a high alpha(A) of 0.91. Moreover, the amount of unreacted monomers remaining in the flow exiting the CSTR was much less than that without the addition of the core monomers. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.