ZrB2-based composite ceramics have great potential for applications at ultra-high temperatures, but the low toughness and poor oxidation resistance of them limit their practical applications. In this work, the Zr, B4C, Al, C and Si raw powders were used to prepare ZrB2-SiC-Zr2Al4C5 composite ceramics by reactive spark plasma sintering. The reaction processes and mechanism were studied. The effects of Zr2Al4C5 content and oxidation temperature on high-temperature oxidation behavior of multiphase ceramics were investigated for revealing the anti-oxidation mechanism. The results indicated that the B4C reacted with Zr to form ZrB2 at 900 ℃, and then the SiC formed at 1 100 ℃. At 1 400 ℃, the Zr2Al4C5 formed from the reaction of Zr3Al3C5, ZrC and Al4C3 which formed at the early initial reaction stage. And the Zr2Al4C5 transformed into Zr3Al4C6 with further increasing temperature. The main phases of the composite ceramics after oxidation are ZrO2, ZrSiO4, aluminosilicate and SiO2 glass. With increasing Zr2Al4C5 content, the surface of the oxide layer of the composite ceramics became uneven, loose and porous, while obvious long strip grains and inhomogeneous distribution of glassy phases were also observed. This study not only provides a new experimental reference for in-depth understanding of the high-temperature oxidation behavior of ZrB2-SiC based multiphase ceramics, but also provides new experimental and theoretical support for developing high-performance ZrB2-SiC based high-temperature composite ceramics.