Abstract: Epoxy has excellent thermal and mechanical properties, but is brittle. Polyethersulphone(PES) and multi-walled carbon nanotubes(MWCNT) were used to toughen epoxy for the preparation of low cost and high performance epoxy system. PES-epoxy blends of different PES contents were prepared and the influence of PES content on mechanical properties of epoxy was discussed. MWCNT/PES-epoxy composites were prepared by using melting method with mechanical agitatioin, high-shearing agitation and ultrasonic dispersion. The tensile properties and fracture toughness were tested. Both the dispersion of MWCNT in resin and the fracture surfaces of broken specimens were observed by SEM. The results show that the comprehensive mechanical properties of PES-epoxy composites can be further improved by adding MWCNT and arrive at the highest value when the MWCNT content is 0.7wt%. At low PES content, the mechanical properties of epoxy with MWCNT content less than 1.0wt% can exceed that of epoxy with 20.0wt% PES. PES and MWCNT have synergistic toughening effects on epoxy.