High producing cost is one of the important reasons that silicon nitride ceramics can’t be widely used today. In this paper, one kind of commercial low-cost silicon nitride powder was used as raw material. High density samples were obtained through pressureless sintering with alumina, yttria and magnesia as sintering aids. The Si3N4 material was tested and the erosion wear rate was measured. It was found that the low cost and dense Si3N4 ceramics exhibited a better erosion wear resistance than the hot-press ceramics produced with the UBE Si3N4 powder and much better then the Cr-26 cast iron. The worn surface was observed with the SEM and the erosion wear mechanisms were analyzed.