Al-ZrO2 composites were sintered in N2 atmosphere at 1000 oC, 1100 oC, 1200 oC and 1300 oC with ZrO2 and Al powders as raw materials. Formation mechanism of AlZrO and ZrAlON phases in Al-ZrO2-N2 systems were investigated by TG-DTA, XRD, SEM and EDS analyses. Results showed there existed new phases of ZrAl3O3N and AlxZr1-xO2-0.5x beside ZrO, ZrN, Al2O3, AlN and intermediate phases of Al7O3N5, Al8O3N6, ZrON, ZrON2, Zr7O8N4 in samples sintered at 1000 oC to 1300 oC. There existed process of mass transfer of ZrO2 in gas phase in samples at high temperature. Dynamics processes of ZrAl3O3N and AlxZr1-xO2-0.5x phases formed in N2 atmosphere at high temperature included contact reaction and ZrAlON sosoloid crystallization.