Micro-ring devices are based on resonance principle and inherently are wavelength selective. Thus it is an important optical component for WDM based applications. To fully utilize the available capacity in an optical network, large full spectral range (FSR) and narrow passband are key performance targets of ring device designs. In this paper we report the design and analysis results of micro-ring filters with 4000+ GHz FSR and 25 to 50 GHz passband, based on symmetric add-drop filter structure. We optimize the passband shape (using a box-like factor), drop loss coefficient and off-resonance through loss via the coupling coefficients and ring loss parameters.