Epoxy resins (EPs) form three-dimensional network polymers upon curing, endowing them with excellent properties while rendering their waste resistant to degradation and recycling. In this study, ground EP micron-sized powder was fluorinated via plasma technology and subsequently incorporated as functional filler for composite reconstruction. Microscopic morphology, chemical composition, and insulating properties of both pristine and modified EP powders/composites were systematically characterized. The experimental results show that after plasma fluorination for 30 min, the agglomeration of small-sized particles of the filler is improved, the crack distribution of the specimen is diversified, and the degree of brittleness is reduced. Compared to the specimens before fluorination, the dielectric constant and volume resistivity decreased, while the breakdown voltage increased significantly. Two-parameter Weibull analysis further confirmed reduced dispersion in breakdown voltage distribution. These findings demonstrate the feasibility of plasma-assisted filler treatment for enhancing EP’s insulation performance while establishing a sustainable recycling paradigm for EP-based composites.