Abstract: The micro structures of epoxy toughened by polyester hot melt adhesive PE30 was studied by SEM.The influence of addition polyester hot melt adhesive PE30 on heat stability of epoxy was studied by DSC,DMC,and TGA.The mechanical properties,including impact strength,bending strength,fracture strength were measured.The results showed that a suitable usage of PE30 is 15%.In the process of curing,the epoxy resin matrix containing polyester hot melt adhesive came out and induced a phase separation,from the single-phase to continuous phase and then to reverse phase.Comparing with the pure epoxy resin,the impact strength and fracture strength were increased by 250% and 127%,respectively.The bending strength and modulus were reduced by 27% and 44%,respectively.The glass transition temperature and starting thermo-gravimetric temperature were reduced by 1.5%,and mechanical loss peak temperature was reduced by 2.5%.It is show that the polyester hot melt adhesive PE30 can significantly toughen the epoxy resin while maintain its thermal performance.