Ferromagnetism of Al-doped 4H-SiC is investigated by means of first-principles calculations. Our results show that Al dopant alone does not introduce any spin-polarization in the doped 4H-SiC, whereas the complex of substitution Al for Si together with a silicon vacancy can induce spin-polarization and local magnetic moment in Al-doped 4H-SiC. The interaction between the local moments results in the ferromagnetism order. The substitutional Al for Si atom introduces hole and mediates spin-polarizations resulting from silicon vacancy to form ferromagnetism in 4H-SiC. (C) 2010 Elsevier B.V. All rights reserved.