The finite-size effects in Coupled Microring Resonator Optical Waveguide (CMROW) are investigated.The transmission and normalized group delay are optimized by inserting antireflection structures in both ends of CMROW.The fit formulas of optimized cross-coupling coefficients in antireflection structures are obtained for both weak coupling and strong coupling.With the fit formulas,the suitable cross-coupling coefficients can be calculated directly and easily.The simulation results show that,optimization can be well realized with the fit formulas.