Abstract: Epoxy resins are widely used in the field of electrical power equipment. With the increase of voltage level and capacity, the demand for high-performance epoxy resin is increasing. The dielectric properties of epoxy resin are closely related to its microstructure. In this paper, tri-functional and tetra-functional epoxy resins are used as network modifiers toinvestigate the changes in glass transition temperature, dielectric constant, and loss factor of the modified epoxy resin system at different contents and temperatures. It is found that the introduction of multifunctional modifiers will enhance the strength of β relaxation process and lead to the reduction of dielectric properties of epoxy resin at lower temperatures. However, the stability of the network structure is increased due to its high cross-linking density. The temperature resistance of the modified epoxy resin is improved, while the α relaxation strength is weakened, indicating the improvement of dielectric properties of the modified epoxy resin at higher temperatures.