Ag-4wt%TiB2 electrical contact materials reinforced with different TiB2 particles were prepared by hot pressing, and the effect of TiB2 particle sizes on the micro-structure and properties of Ag-4wt%TiB2 electrical contact materials were studied. The microstructure and arc erosion morphology of Ag-4wt%TiB2 electrical contact materials were characterized by a scanning electron microscope and a confocal laser scanning microscope, and the relative density, hardness and electrical conductivity were tested as well. The results show that the hot pressing is favorable to improve the relative density of Ag-4wt%TiB2 electrical contact materials.With decrease of TiB2 particle size, the electrical conductivity constantly increases, while the hardness increases and then decreases. The fine and well distributed TiB2 particles are beneficial for the improvement of arc erosion resistance. The Ag-4wt%TiB2 contact material presents shallow erosion pits, large erosion area, and short arcing time.