This study simulates the surface-tip-enhanced Raman scattering (SERS-TERS) model of a stepped tip with a silver film and a silver-nanoparticle-active substrate. The simulation is established by the finite-difference time-domain method. The near-field electric field distributions of different types of needle tips and substrates are numerically calculated under the same conditions, verifying the effectiveness of the designed method in the Raman scattering enhancement. Next, the electric field intensity of the model is systematically analyzed under different influencing factors: the curvature radius of the tip, the thickness and height of the silver film on the tip, the diameter of the silver nanoparticles, the gap between the tip and the silver nanoparticles, and the incident angle. The field enhancement factor is maximized at a tip-curvature radius of 5 nm, a silver-film thickness of 25 nm, a silver-film height of 300 nm, a silver-nanoparticle diameter of 55 nm, a 1 nm gap between the tip and silver nanoparticles, and an incident angle of 45°. The largest enhancement factor is of the order of magnitude of 107. The simulation results provide an important theoretical basis and experimental guidance for preparing high-efficiency tip and TERS active substrate structures.