Zirconium nitride (ZrN) ceramics were prepared via hot pressed sintering (HP) at 1750 ℃ in N 2 atmosphere with ZrO 2–Y 2O 3 as sintering additive. X-ray diffraction was applied to analyze the phase composition of the as-prepared ceramics to study the high temperature phase relation in ZrN–ZrO 2–Y 2O 3 ternary system and establish ZrN–ZrO 2–Y 2O 3 ternary phase diagrams. The results show that ZrN and tetragonal ZrO 2 (t-ZrO 2) solid solution, face-centered cubic ZrO 2 (c-ZrO 2) solid solution, body-centered cubic Y 2O 3 (c-Y 2O 3) solid solution coexist in the system of ZrN–ZrO 2–Y 2O 3.