A new kind of metamaterial, an array of periodic gold rod pairs standing on gold substrate, is introduced in this paper. A commercial electromagnetic mode solver, the High-Frequency Structure Simulator, is employed to explore the propagation property of electromagnetic waves in this system. When an S -polarized electromagnetic (EM) wave propagates along the substrate surface, strong magnetic resonance is produced in the far-infrared regime. Based on the simulated S parameters, effective refraction index is retrieved and negative value is obtained over the wavelength range from 49.2 microm to 66.7 microm. A wedge made of this metamaterial with an inclined angle 26.6 degrees is designed. An observable negative refraction behavior of EM wave is attained in this structure at wavelength 61.2 microm. The refractive index is calculated by Snell's law and it is consistent with the retrieved results quite well. This provides direct evidence for the negative refraction property.