A Photonic Crystal Ring Resonator (PCRR) based Channel Drop Filter is designed using Two Dimensional (2D) square lattice PC silicon rods in air host. The normalized transmission spectra for single-ring and dual-ring configurations have been investigated by using the 2D Finite Difference Time Domain (FDTD). The filter characteristics such as dropping efficiency, resonant wavelength and Q factor are numerically analyzed for single ring and dual ring PCRR. It is noted that the dropping efficiency and Q factor of single ring circular PCRR with scatterer rod are 100% and 186.75, respectively. The backward dropping is observed in single ring PCRR whereas forward dropping are noticed in dual ring PCRR based CDF. The Photonic Band Gap (PBG) with respect to structural parameters such as radius of the rod, lattice constant and delta, and propagation modes in periodic structure are calculated by Plane Wave Expansion (PWE) Method.