In order to improve the performance of surface-enhanced Raman scattering(SERS) substrate, silver nanowire substrate was used in this paper. The substrate and diameter of silver nanowire were optimized based on finite element analysis software. The results show that when the substrate is gold film, the hot spot electric field modulus of the substrate is the largest, indicating that it has the best enhancement effect. At the same time, the enhancement effect of silver nanowires with different diameters on the gold substrate was designed and studied. The results show that when the radius is from the 10 nm to 75 nm, the enhancement effect is first enhanced and then weakened. When the radius of the silver nanowires is 45 nm, the enhancement effect is the best. Based on the above research results, a gold film-silver nanowire substrate was prepared, and the prepared substrate was applied to the detection of furfural concentration in transformer oil. The minimum detection limit of the prepared substrate for furfural in transformer mineral oil can reach 1.5 mg/L. It is of great significance to realize the monitoring of transformer operation status.