A variety of combinations of Y₂O₃ and Al₂O₃ were used as sintering aids in the fabrication of Si₃N₄ ceramics via gas pressure sintering (GPS). Based on the prediction of the residual thermal stress at the interface, the influence of crystal phases on the wear properties of Si₃N₄ ceramics was analyzed. As a result, with the increase of Y₂O₃ addition from 1 to 9 wt%, there are four kinds of crystal phases being firmly discovered in the sample, Y₂Si₂O₇, YSiO₂N, Y₄Si₂O₇N₂, and Y₂Si₃O₃N₄. The crystal phases of Y₂Si₂O_7, YSiO₂N, and Y₄Si₂O₇N₂ inhibit the particle flaking during the friction process, which greatly inhibited the progress of the abrasive wear, and optimize the wear resistance of silicon nitride ceramics. According to Selsing's model, it can be predicted that the interface residual thermal stress caused by the intergranular phase Y₂Si₃O₃N₄ is 22–35% higher than that caused by the other three intergranular phases. The crystal phase Y₂Si₃O₃N₄ intensifies the shedding of grains during wear, and reduces the wear performance of silicon nitride ceramics. In addition, the silicon nitride ceramics with 5wt% Y₂O₃ show better wear resistance, and the wear rate is 1.8 × 10⁻⁶ mm³ N⁻¹ m⁻¹.