A square-lattice photonic crystal structure was proposed based on circular-ring cylinders and thin cross plates.The calculation process and the influence of operating parameters on the absolute bandgaps were presented.It is demonstrated through plane wave expansion method combined with cut-and-try method that its maximum relative absolute photonic bandgap reaches 19.026%,which is 10.181% and 712.035 9% higher than that in a PhC made of solid cylinder and connecting veins and that in a PhC made of dielectric rings,respectively.And there exist optimum values for the outer radius of the circular-ring cylinders,the relative ring thickness,and the thickness of the cross plates.Furthermore,the influence of the thickness of the cross plates on the relative APBG is quite sensitive.