Epoxy composites, as key insulating materials for high-voltage electrical equipment, are operated at high temperatures and high mechanical stresses for a long period of time, so electrical epoxy composites need to meet the requirements of high thermal conductivity and high toughness. It is found that the filling of high proportion of inorganic thermally conductive fillers can significantly enhance the thermal conductivity of epoxy composites, but it also leads to the reduction of mechanical properties of epoxy composites. This paper is devoted to exploring the mechanical property enhancement method of high filler and high thermal conductivity electrician epoxy composites by introducing glass fibres into the epoxy composites for toughening and enhancing their mechanical strength. The experimental results show that when the addition ratio of glass fibres reaches 10phr, the mechanical strength of epoxy composites is improved the most, the bending strength is increased to 73.09MPa, the tensile strength reaches 39.84MPa, and the impact strength reaches 17.87kJ/m2, which is increased by 6.7%, 8.9% and 22.9%, respectively, compared with the unmodified epoxy materials.