The transmission characteristics are analyzed, and the general formulas of the transmission functions are presented for the microring resonant wavelength multiplexer (MRRWM) with 1×N channels in terms of the coupled mode theory. Using the results of parameters optimization, the numerical modeling is performed for a polymer MRRWM around the central wavelength of 1.55 μm with the wavelength spacing of 5.6 nm and 8 vertical output channels. The computed results show that the device has an exact output spectrum, the insertion loss is small and determined mostly by the transmission loss for microrings with radius R greater than 10 μm. For the case of the amplitude coupling ratio of 0.2, the device designed possesses some excellent features including the free spectral range of 18 nm, smaller insertion loss less than 0.57 dB, lower crosstalk below -18.5 dB, 3 dB-bandwidth of 0.25 nm, and weaker background intensity of 3.8×10-4 for every output vertical channel.