Alkali metal and alkali earth metal clathrate-based compounds have attracted massive attentions due to their outstanding electronic and mechanical properties. In this work, the structural, physical and mechanical properties of AlB₃C₃ in clathrate-based sodalite structure are systematically studied within ab initio electronic structure framework. Our results show that the lattice constant of AlB₃C₃ is a = 4.731 ?, and it exhibits metallic behaviors with the evidence that several bands crossing the Fermi level at ambient pressure. The B atoms and C atoms form strong sp3 covalent bonds in the framework. Moreover, the elastic contants satisfy the mechanical stability criteria, and the bulk modulus is 228 GPa. Our findings provide insights of metal boron carbide componds whose frameworks consist of strong covalent bonds.