Mechanical behavior and deformation mechanism of Al nanowire along different crystal orientations are investigated with molecular dynamics simulation. They are compared with those of FCC metal nanowires with lower fault energy such as Ni, Cu, Au and Ag under same computational conditions. It is found that the elastic module of Al nanowire along different crystal orientations displays a relationship of E_[111] > E_[110] > E_[100], which is generally true in FCC nanowires. The yield stress of Al nanowire along different crystal orientations displays a relationship of σ_y[100] > σ_y[111] > σ_y[110], which is not generally true in FCC nanowires. Furthermore, deformation mechanism of Al nanowire along crystal orientations is clarified according to the evolution of microstructures. It is compared with that of nanowires of Ni, Cu, Au and Ag. It was found that it is difficult to predict deformation mechanism accurately with Schmid factor and stacking fault energy for Al nanowire with high fault energy in small scales.