In order to strengthen the effect of Raman spectroscopy in bio-detection and sensor fields,the requirement to optimize the balance between signal enhancement and reproducibility in surface enhanced Raman scattering （SERS）is stimulating the development of novel substrates for enhancing Raman signals.The Raman enhancements produced from a variety of nanometer SERS substrates with different size,space,and shape are simulated and optimized by finite element electromagnetic simulation.A theoretical comparison between four major generic types of SERS substrate has been performed and the results are presented and discussed.The results of the simulation are consistent with the published experimental data of similar substrates.