Complete band gap of two-dimensional photonic crystal structure with four different scatterers (circle, hourglass, wing, duck) are simulated. The symmetry of the four scatterers in turn reduce. The results show that the duck-shaped scatterers of photonic crystals are more likely to produce complete band gap than other shapes of scatterers. The influence of dielectric constant and the geometric parameter of duck-shaped scatterer on the complete band gap is studied. The results show that when the dielectric constant is 26.6, the big semicircular radius is 0.331 μm , and the radius of small semicircular is 0.535 times that of the big semicircular, the value of complete band gap reaches the maximum value of 0.0583 (wa/2πc).