The invention discloses an epoxy resin encapsulating material as well as a preparation method and application thereof, and belongs to the technical field of electronic materials. The epoxy resin encapsulating material is prepared from the following raw materials: a resin part, namely a bisphenol A epoxy resin, a dicyclopentadiene phenol-type epoxy resin, a multifunctional diluent, a filler, a silane coupling agent and auxiliaries, and a curing agent part, namely methyl nadic anhydride and/or methyl tetrahydrophthalic anhydride, a cycloaliphatic epoxy resin and an accelerant; the resin part is mixed with the curing part to obtain the epoxy resin encapsulating material. According to the encapsulating material, the dicyclopentadiene phenol-type epoxy resin is added to the resin part, the silane coupling agent is applied to activating the filler in combination with the multifunctional diluent, and the cycloaliphatic epoxy resin is added to the curing part, and therefore, the finally obtained encapsulating material has the characteristics of high temperature resistance and high humidity resistance. The encapsulating material is used for preparing a capacitor, and consequently, the capacitor is enabled to be stable in capacity, small in change tolerance and longer in service life under the conditions of a high temperature, high humidity, and running with load after being powered on.