The Ag-TiB₂ contact materials with Ag powders of different sizes were prepared by spark plasma sintering. The relative density, electroconductivity, and hardness of Ag-4wt% TiB₂ contact materials were measured, and the arc erosion behavior of the contact materials was analyzed under the vacuum condition. The surface morphologies of Ag-4wt% TiB₂ contact materials after arc erosion were characterized by the scanning electron microscope. The arc duration was determined by the discharged waveform recorded by a Tektronix TDS-2014 dual channel digital memory oscilloscope, and the arc erosion mechanism was discussed. The results show that the relative density, electroconductivity, and hardness of Ag-4wt% TiB₂ contact materials are increased with decreasing the Ag powder size. Furthermore, the Ag-4wt% TiB₂ contact materials prepared from fine Ag powder have longer arc duration, larger erosion area, and shallower erosion pit, suggesting that the fine Ag powder is beneficial for arc dispersion and the improvement in arc erosion resistance.