In this paper an accurate analysis of two-dimensional (2D) coupled ring resonators based on high index-contrast is carried out. The normalized transmission spectra for single-ring and double-ring configuration have been investigated by using a robust and accurate Multiresolution Time Domain (MRTD) technique with conjunction with uniaxial perfectly matched layer (UPML) absorbing boundary condition that rigorously terminate the computational window. The resonant-mode quality factors (Q), free spectral range (FSR) are numerically investigated. The variation of the structure parameters such as the symmetric and asymmetric gap size (g) lead to dramatic changes of Q and the extinction ratio of the device. Studies of the transmission characteristics for the ring diameter of 3.4 μm shows the possibility for achieving Q’s in several thousands and FSR of 9 THZ (80nm) in the 1.55 μm wavelength range.