Abstract A novel amine with flexible polyoxypropylene side chain (AFPE) was synthesized and characterized with FT-IR and NMR. Then, AFPEs with different molecular weight were used as a curing agent for diglycidyl ether of bisphenol A (DGEBA), and non-isothermal reaction was detected with DSC. The kinetic parameters of the curing process were determined by Málek method. A two-parameter (m, n) autocatalytic model (Šesták–Berggren equation) was found to be adequate to describe the reaction-controlled kinetics of the studied epoxy resins, yet was insufficient in depicting the diffusion-controlled kinetics of the epoxy resins. The values of Ea depended on the molecular weight of AFPEs, and increased with longer polyoxypropylene chain length in the AFPE. Dynamic mechanical analysis of AFPEs modified DGEBA/diethylenetriamine systems found that with the increasing molecular weight of AFPEs, α relaxation temperature, β relaxation temperature and crosslinking density decreased, while impact strength and elongation at break improved. From scanning electron microscope, tensile surfaces were rougher and sizes of cavities in the surface became larger with the increasing molecular weight of AFPEs. Our study showed that AFPE was a novel and effective toughening agent for epoxy resins.