Abstract: Colloidal carbon spheres were prepared by a hydrothermal method using glucose as a raw material, and then they were activation treated by phosphoric acid.The active carbon spheres (ACs) achieved the maximum specific surface area of 1354 m2/g.ACs were characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy.A flame retardant epoxy system was fabricated by incorporation of ACs along with ammonium polyphosphate (APP), and its synergistic flameretardant performance was investigated by limiting oxygen index, vertical burning experiment and micro calorimetry.The flameretardant mechanisms were studied by thermogravimetric analysis and scanning electron microscopy for the char residue.The results indicated that the flame retardant epoxy system achieved a V-0 classification in the UL 94 vertical burning test when 0.1 wt % of ACs and 2.9 wt % of APP were added.Moreover, its peak heat release rate decreased by 44.1 % in comparison with pure epoxy resin.