Our numerical simulation results show that if a compound structure is composed of a lattice with a larger periodic constant and a lattice with a small periodic constant, the lattice with larger periodic constant will play the role of defects. The frequencies of defect modes are dependent on the rod radius (r2) of square lattice with a larger periodic constant, and the relationship of the defect modes and r2 is almost independent of a2. The defect mode is dependent on incidence angle when a22. Furthermore, by optimizing the size of the rods (r2) of the larger periodic lattice, single defect mode, multiple defect modes with equal or different frequency spacing, including single polarization or TE and TM overlap defect mode, can be gotten respectively. The transmissivity of the defect modes are inversely proportional to a2.