We take the square lattices with elliptic and square rods respectively as exampies,to illuminate the effect of shapes and orientations of rods on the photonic band gap in two-dimensional square lattices. Two cases have been discussed that the wave vectors are in the periodic plane and off the periodic plane. By compare,we find that the changes of the shapes and orientations of rods will make the photonic-crystals which have no complete band gap present a complete band gap or turn low complete band gap in low frequency range to a higher frequency range. We also find that wave vector in and off periodic plane will influence the lattices composed of elliptic rods much larger than that composed of square rods.