Abstract: Phononic crystal is a novel functional material with acoustic band-gaps. We study the band structure of 2D phononic crystal using the plane wave expansion method. The crystal is composed of a square array of scatterers embedded in an epoxy host, and the scatterers have square cross sections. The results show that the band-gaps of this system can be adjusted by changing the scatterers′ tropism. When the filling rate is low, with the increase of the scatterers′ rotation angle, the band-gap width initially becomes narrower and then widens gradually, while at high filling rates, the band-gap width increases slightly at first and then decreases as the scatterers′ rotation angle increases.