Raman scattering and surface-enhanced Raman scattering (SERS) have attracted the attention of researchers due to the great potential applications in various research fields, including biomolecular sensing, analytical chemistry, surface science and material science. In order to improve the enhancement effect of the SERS substrate, the electric field enhancement of rice-shaped silver monomer, dimer, and trimer nanoparticles was simulated by the finite difference time domain method under different polarzation directions. The influence of the shape and spacing of the nanoparticles on local elecric field intensity were also studied and analyzed. On the above basis, the causes of electirc field enhancement were discussed in detail. The result shows that the electric field distributions of rice-shaped silver nanoparticles are different by changing the shape and spacing of the nanoparticles, as well as the polarization direction. The tip of the rice-shaped silver nanoparticle with long axis 300 nm, minor axis 36 nm and spacing 2 nm can produce maximum electric field enhancement when the incident polarization direction is parallel to the long axis. Moreover, due to the strong coupling between the nanoparticles, there is an obvious enhancement effect in the case of top to top configuration, and the obtained SERS enhancement factor (EF) is up to 2.4×1011. The conclusion provides theoretical basis for the preparation of silver nanoparticles in the SERS experiments.