In this paper, a small size edge-reflected surface acoustic wave (SAW) IF filter based on a lithium tantalate piezoelectric substrate is modeled and simulated by COMSOL Multiphysics finite element simulation software, and the finite element simulation analysis of the physical fields of solid mechanics and electrostatics is carried out for this SAW filter. At the same time, the effects of electrode material and electrode thickness on the resonant and anti-resonant frequencies of the admittance curves are discussed. It is demonstrated that the electrode thickness can affect the parasitic resonance of the admittance curves. The thickness of the electrode at the weakest resonance in the admittance curves is selected as the optimum thickness of the electrode. Finally, the Al with a thickness of 1.6 μm is chosen as the electrode of the small size SAW filter and the simulation analyses of the transmission responses under different substrate end face positions are carried out. The conventional 2D FEM simulation results show that the device has a center frequency of 126.35 MHz, insertion loss of -2.57 dB, and -3 dB bandwidth of 3.3 MHz when the end face of the substrate edge is 0 from the edge of the IDT. The simulation result has a high matching degree with the response obtained by COM model simulations, which further proves that the reflection of the large dielectric constant substrate end face can be equated to a strongly reflected reflective strip from the perspective of theoretical simulation.