In this paper, a micro-ring resonant filter(MRRF),consisting of two cascaded coupled racetrack rings and using MMI as input/output coupling structure, was designed and fabricated on the Si substrate by using a UV sensitive polymer material SU-8 as the core material of the waveguide and polymer material CYTOP as the bottom cladding layer. According to the scanning electron microscope (SEM) results, the cross sectional size of waveguide of the device is 2 μm×1 μm, which is in accordance with the designed value, the waveguide shows high sidewall quality. The propagation loss of straight optical waveguide is measured to be 2.0 dB/cm at 1550 nm wavelength. The near field optical pattern from the output port of MMI structure and the output spectrum of the MRRF were obtained. The measured results show that the power ratio of the MMI was close to 50∶50 in a relatively wide range of wavelengths, and the filtering was realized, the measured free spectral range FSR of device is about 0.94 nm, which is close to the designed value. The study results show that it is simple and feasible for fabricating MRRF with fine waveguide by using SU-8.