Si₃N₄-ZrO₂-La₂O₃ ternary system were prepared via solid-state reaction at 1500 ℃ for 1 h with N₂ protection, yielding coexistence phase of ZrN and lanthanum-based compounds, such as La_4.67Si₃O₁₃, La₅Si₃NO₁₂, La₄Si₂N₂O₇, LaSiNO₂, and La₂Zr₂O₇. Since the generated ZrN and lanthanum-based compounds are not located on the triangle plane of Si₃N₄-ZrO₂-La₂O₃ system, it is necessary to add SiO₂ to extend the ternary into quinary system of Si₃N₄-SiO₂-La₂O₃-ZrO₂-ZrN. After the phase diagram of this quinary system is confirmed and presented, the phase diagram of La₂O₃-SiO₂-ZrO₂ ternary subsystem at 1570 ℃ is further proposed for the first time. In addition, La₂O₃ in the Si₃N₄-ZrO₂-La₂O₃ ternary system can help to simulate the substitution reaction between Si₃N₄ and ZrO₂ to produce ZrN.