Silane coupling agent (KH-550) was used to modify milled glass fiber (MG) and hollow glass beads (HGB) to prepare organosilicon-modified epoxy resin (YE). Modified MG, modified HGB, and modified MG-HGB were used as reinforcing fillers to fill YE, resulting in three types of YE encapsulating material. The effects of reinforcing materials on the mechanical properties of YE encapsulating material were compared. The results show that when the water consumption for preparing the organic silicone intermediate is half of the theoretical water consumption, the mechanical properties of the YE encapsulating material are optimal. Compared with the epoxy resin (EP) encapsulating material, the tensile strength is increased by 28.1%, the bending strength is increased by 35.3%, and the impact strength is increased by 266%. Compared with the YE encapsulating material, the impact strength of the YE/modified MG material is decreased, while the impact strength of the YE/modified HGB material is increased. The mechanical properties of the YE/modified MG-HGB material vary with the proportion of modified MG, with tensile strength and impact strength first increasing and then decreasing, while bending strength continues to increase. When the mass ratio of YE∶modified MG∶modified HGB is 100∶100∶3, the mechanical properties of the material are optimal, with tensile strength increased by 137%, bending strength increased by 42%, and impact strength increased by 90%.