The generalized planar fault (GPF) energies of various slip systems in γ-TiAl intermetallics are studied by using molecular dynamics (MD) method. The unrelaxed and relaxed GPF curves of various slip systems are compared. It was show that the γ-TiAl has fewer mobile slip systems than the fcc crystal. It is also found that the γ-TiAl intermetallics would exhibit brittle behavior at ambient temperature. The relaxed generalized stacking and twinning fault energy curves of (1/6)〈112〉{111} twinning system are obtained. By analyzing the unstable stacking fault energy γusf, the stable stacking fault energy γsf, and the unstable twinning fault energy γutf, it can be predicted that the major deformation mechanisms are twinning (1/6)〈112〉{111} and ordinary dislocation slip (1/2)〈110〉{111}, as well as superdislocation slip (1/2)〈011〉{111}.