Crystalline structure of a sample of Alumina (Al2O3 – reinforced epoxy) at (4% and 8%) has two prominent peaks at point (17°) and (19.5°) with miller vectors (111) and (220), respectively. These results are corresponding to crystalline cubic and notes growing of crystallization. The spectrum of (XRD) showed increase in crystalline size which means an increase in randomization and a lack of crystallization amorphous at (6%) (Al2O3). This result showed increase in crystalline size which means an increase in randomization and a lack of crystallization amorphous. Epoxy matrix reinforced by particles of silica (SiO2) and alumina (Al2O3) with different fractions were investigated for electrical properties such as dielectric constant, conductivity and dielectric loss index. This result showed effect of additional (SiO2, Al2O3) is small concentration except (2% SiO2) has large effect.