Abstract: By the flexural test of fly ash cenospheres (FACs)/epoxy resin composites,the effect of cenospheres content,particle size and grading ratios on flexural properties of the cenospheres/epoxy resin composites were studied,and the flexural mechanism was analyzed through the flexural fracture morphology.The results show that the addition of cenospheres significantly affects the flexural strength of cenospheres/epoxy composites.With the increase of cenospheres content,the flexural strength of the composites increases first and then decreases and it reaches the maximum when the content of cenospheres is about 15wt%.With the decrease of particle size of the cenospheres,the flexural strength of cenospheres/epoxy composites increases.The smaller size of cenospheres is more benefical to improve the flexural strength of composites.So the flexural strength of composites filled with grading cenospheres is mainly affected by small particle content in grading cenospheres,and with the larger proportion of small size cenospheres,the higher flexural strength of cenospheres/epoxy resin composites can be obtained.