Using　the　symmetry　reduction　method,　elliptical　steel　cylinders　are　periodically　arrayed　in　air,　which　forms　the　two-dimensional　triangular　lattice　phononic　crystal.　The　band　structures　are　computed　by　the　plane　wave　expansion　(PWE)　method.　Numerical　results　show　that　the　degeneracy　at　high　symmetry　point　of　Brillouin　zone　can　be　lifted　by　using　elliptical　scatters,　which　lowers　the　frequency　for　opening　band　gaps.　Besides,　the　lower　symmetry　is,　the　easier　it　is　to　open　wide　low　frequency　band　gaps.　In　contrast,　the　higher　it　is,　the　easier　it　is　to　open　wide　high　frequency　band　gaps.　These　results　can　be　used　in　industrial　design　to　isolate　low　frequency　noise.