AlN-SiC multiphase ceramics possess robust mechanical strength, high thermal conductivity and good oxidization resistance, and show great potential as the matrix material of fiber reinforced ceramic matrix composites. In this work, AlN-SiC multiphase ceramics were fabricated via low temperature reactive melt infiltration of Si-Al alloy into porous C-Si₃N₄ preforms. Influence of Si-Al source on the melt infiltration process was studied, and impact of residual silicon on the mechanical and thermal properties of the AlN-SiC ceramics was investigated. It was found that an Al-O layer was in-situ formed at the interface between Si-Al melt and C-Si₃N₄ preform, when Si-Al powder was used as the infiltration medium. This seriously retarded the melt infiltration process and made the penetration of Si-Al melt into the C-Si₃N₄ preform hardly possible. However, when Si-Al ingot was used as the infiltration medium, a well infiltration of Si-Al melt into the C-Si₃N₄ preform occurred, which led to the formation of dense AlN-SiC ceramics. Mechanical and thermal property measurements indicated that the strength of the AlN-SiC ceramics was significantly improved as the residual silicon content in it was reduced, while a reverse trend was observed for the thermal conductivity. AlN-SiC ceramics with 4%(in mass) residual silicon showed a high strength of 320.1 MPa, nearly comparable to that of conventional reaction bonded SiC, although its thermal conductivity was modest (26.3 W·m^-1·K^-1). The fundamental reasons for the above phenomena were discussed. This study is of great significance for the preparation of SiC_f/AlN-SiC composites by low temperature reactive melt infiltration.