It completely decomposes to a mixture of a tetragonal phase and a Cu9Al4 phase. Electronic structure, magnetism and face stability of new Mn-based Heusler alloys Mn2CuAl has been studied and synthesized by first-principles calculations and by the melt-spinning method. Firstly, the calculations suggest that Mn2CuAl crystallizes in the Hg2CuTi type of structure, in which the Cu atoms have Al as nearest neighbors. As a consequence, the Mn atoms occupy two nearest neighbors’ sub lattices A and B. Like the well knownHeusler alloyCu2MnAl, the magnetic moment of ,Mn2CuAl also comes from the 2Mn atoms in the lattice, while the Cu atom is almost nonmagnetic .At equilibrium lattice constant, Mn2CuAl is a ferrimagnetic with moment of 0.22uB. The partial spin moments of Mn (A) and Mn (B) are -3.52uB and 3.74uB, respectively. The small total moment comes from the antiparallel configurations of the Mn partial moments. With a small contraction of the lattice, the total moment becomes near zero and half-metallic antiferromagnetic state is observed. Secondly, It has an ordered bcc structure and is a ferrimagnet with a saturation moment of 1.44mB/f.u. at 5 K. The magnetization mainly comes from the contributions of the antiparallel aligned Mn spin moments. A compensation point is observed at 630 K, indicating the antiferromagnetic between the two Mn sublattices. The Curie temperature of the ribbons is 690 K When heated to 740 K, the Mn2CuAl.