The effect of basis configuration on acoustic band structure in two-dimensional complex phononic crystals （PCs） was investigated. We found that when the basis configuration was changed, the irreducible Brillouin zone （BZ） of PCs might be changed too，and part of band extrema were no longer on the high-symmetry lines. In particular，the PCs with some basis configurations were forced to render the whole first BZ irreducible. Therefore，besides the high symmetrical PCs，only by throughout investigation of the BZ can we obtain the authentic band structures and band gaps for the lower symmetrical PCs with complex crystal lattice.