Oil-paper insulation equipment is one of the key components in power systems, and accurately assessing the aging status of electrical equipment’s oil-paper insulation is crucial for ensuring the safety of power grids. Acetone is an important indicator of the aging process of insulation paper, and the rapid, sensitive, and accurate determination of acetone content dissolved in insulation oil is of significant importance in evaluating the aging of oil-paper insulation systems. In this study, a surface-enhanced Raman scattering (SERS) substrate based on silver nanowires (AgNWs) decorated with gold nanostars (AuNSts) was successfully prepared on a silicon-gold (Si-Au) film surface using the ion sputtering method. This substrate was utilized for rapid assessment of acetone content in insulation oil. Morphological characterization of the substrate by scanning electron microscopy revealed that the dual-metal satellite-surrounded structure formed by smaller gold nanoparticles sputtered onto the larger surface area of AgNWs not only effectively enhanced surface plasmon resonance but also provided a protective barrier layer for AgNWs, significantly improving the overall antioxidant performance of the substrate. SERS detection results showed that compared to Si-Au, Si-Au-AgNWs, and Si-AgNWs-AgNts substrates, the Si-Au-AgNWs-AuNSts substrate exhibited superior SERS performance, with the lowest detection limit of 40 mg·L^-1 for acetone dissolved in insulation oil after water (H₂O) extraction. Moreover, the substrate demonstrated high consistency and stability, with an RSD value of 4.87%, and after 30 days, the target peak signal only decreased by 6.14%. This method provides an effective approach for achieving reliable on-site detection of acetone dissolved in oil.