In order to reveal the structural evolution process of hollow glass microsphere（HGM） at high temperature，and further grasp the thermal ablation mechanism of HGM in composites at high temperature，SEM，TG and EDS were used to characterize the micromorphology，thermal weight loss and distribution of elements of HGM heated at 500~1 400 ℃.And HGM reinforced EPDM composites were prepared，and the ablation rate and microstructure of carbonated layer were characterized by oxyacetylene ablation test and SEM.The results show that the chemical properties of HGM are stable within 1 400 ℃，and the weight loss rate，element composition and distribution are basically the same as the initial properties.After heating at 500~700 ℃，HGM appears broken，and with the increase of temperature and time，the broken rate increases.The high temperature breakage resistance of HS46 and HS38 is better than that of HS22.With the further increase of temperature，the melt first transforms into porous structure and then into non-porous dense melt.In EPDM composites，HGM is broken under the action of oxyacetylene flame and a large number of small diameter microspheres appeares.Under the effect of efficient heat insulation of the carbonized layer，the HGM on the back of the carbonized layer is basically a complete sphere structure，but part of it shrinks and wrinkles at high temperature；HGM effectively reduces the linear ablation rate of EPDM composites by about 20%~30%，and the smaller the particle size，the more obvious the effect.