The structure of 2D rods PhC CCW is studied, and it is found that the group velocity discreases quikly with the increase of lattice number between two rod defects. When 7×7 supercell unit is chosen, the largest group velocity νg-max of the guided mode is about 1/251 times that of photonic crystal line defect waveguide. Radius of the four rods around the cavity of the 7×7 supercell unit are adjusted, νg-max of the new strcture can reach 589×10-4c, and it's about 1/5 that of unadjusted structure. Finally, by making comparisons, it is found that the structure has the best slow-light characteristic when the radius of the up and down rods are changed.