Five secondary amine terminated poly(ester-amine)s(defined as PEA)with controlled molecular structures were synthesized through reacting excessive piperazine with phthalicdiglycol diacrylate(PDDA)and 1,1,1-trimethylolpropane triacrylate(TMPTA)at a constant secondary amine/acrylate group ratio of 1.5/1 and at different PDDA/TMPTA molar ratios. Both IR and ~(?)H-NMR spectra indicated that all acrylate groups were consumed in the reaction,based on which the structural parameters were calculated from the ~(?)H-NMR spectra.With decreasing PDDA/TMPTA ratio,the content of secondary amine,degree of branching,molecular weight,T_g and T_d increased accordingly.These polymers were further used as both crosslinkers and flexibilizers for a linear epoxy resin E51 to form cured films under ambient condition.The gel content, relative hardness and T_g of the resulting films increased as PEA molecules changed from linear to highly branching structures.Due to the flexibility of PEA molecules,all the films possessed excellent mechanical performance. Five secondary amine terminated poly (ester-amine) s (defined as PEA) with controlled molecular structures were synthesized through reacting excessive piperazine with phthalicdiglycol diacrylate (PDDA) and 1,1,1-trimethylolpropane triacrylate (TMPTA) at a constant secondary amine / Both IR and ~ (?) H-NMR spectra indicated that all of the acrylate groups were consumed in the reaction, based on which the structural parameters were calculated from the ~ (( ?) H-NMR spectra. Reduced PDDA / TMPTA ratio, the content of secondary amine, degree of branching, molecular weight, T_g and T_d increased accordingly. The polymers were further used as both crosslinkers and flexibilizers for a linear epoxy resin E51 to form cured films under ambient conditions. The gel content, relative hardness and T_g of the resulting films increased as PEA molecules changed from linear to highly branched structures. Subject to flexibility of PEA molecules, all the film s possessed excellent mechanical performance.