Abstract: Different content (10wt%-40wt%) Al₂O₃ micro-particle modified epoxy composites were prepared by blended solution method. The influence of Al₂O₃ micro-particle content on thermal and electrical conductivity of the composites was studied. The results show that when the content of Al₂O₃ micro-particles were 10wt% and 20wt%, the Al₂O₃ micro-particles were well dispersed in the matrix. With increasing content of Al₂O₃ micro-particles, the micro-particles contacted with each other and agglomerated. With increasing content of Al₂O₃ micro-particles from 10wt% to 40wt%, the thermal conductivity of the composites increased from 0.30 W·m^-1·K^-1 to 1.11 W·m^-1·K^-1 at room temperature; the glass transition temperature increased from 115.44℃ to 122.89℃; the linear expansion coefficient decreased from 56.86×10^-6 K^-1 to 34.86×10^-6 K^-1; the resistivity decreased from 4.27×10¹⁰ Ω·cm to 3.01×10¹⁰ Ω·cm; the dielectric constant increased from 7.97 to 10.36 at 50 Hz; the dielectric loss factor at high frequency larger than 100 Hz was basically unchanged.