In order to improve the dispersion and uniformity of the alumina filler in the organic matrix， enhence the interface affinity between alumina and organic epoxy resin，obtain a composite material with excellent performance，silane coupling agent was used to modify the surface properties of alumina filler for epoxy casting.The effects of coupling agent type，dosage，modification methods and process conditions on the oil absorption rate，activation index of filler alumina，the working time and viscosity of epoxy pouring system were investigated.The experimental results showed that the oil absorption value of the alumina filler，the viscosity and workinge time of the epoxy casting system were effectively improved by the coupling agent.According to the experiment results，most appropriate test conditions were that 0.75% of coupling agent B modified with dry modification was selected as the coupling agent，the reaction temperature and pH value were 105 ℃ and 4，respectively.Under the experiment conditions as described above，the activation index of the obtained alumina was 98.2%，the oil absorption rate was reduced by 19%，and an increase in the working time to 52%.The phase structures and microstructural properties of the modified filler alumina powder were investigated using X-ray diffraction and scanning electron microscopy，respectively.The results indicated that the internal crystal structure of the modified alumina filler powder were not changed，and the dispersion of powder was uniform.