Based on the plane wave expansion method (PWE),sonic wave band gaps in the twodimensional threecomponent phononic crystals composed of square array of tetrachloromethane square columns(cylinders) coated by water layers embedded in a mercury host are investigated. The calculation results show that the cylinders more easily get higher frequency band gaps than square rods do at the same filling fraction.The calculations also exhibit that whether the shape of the scatters is square columns or cylinders, the relative bandwidth of the first gap is stable,but the relative width of the second gap is greatly influenced by the shape of the scatters.The relative bandwidth of the first gap with square becomes narrower than that with circular.It is suggested that the frequencies of the band gaps can be controlled by the shape of the scattering objects.This could be of importance in designing phononic crystals of liquid systems and finding their optimum operation conditions.