The insulating tie rods in gas insulated switchgear(GIS) need to withstand extremely high fracture recovery voltage and high-frequency mechanical loads during operation, and the probability of internal breakdown problems is high, which affects the reliability of the equipment and the safe operation of the power grid. The paper takes two-dimensional glass fiber reinforced epoxy resin composites as the research object, establishes the mechanical model of composites on various scales, carries out the finite element simulation of the fine model and microscopic model under the tensile load in various directions, researches the damage evolution law of the composites on various scales, and prepares the specimen samples of the glass fiber epoxy resin composites, and researches the relationship between the composite material’s dielectric strength and the evolution of the internal damage.