A new tunable microwave photonic filter combining optical waveguide micro-ring resonator and Mach-Zehnder interferometer (MZI) is proposed to realize single sideband filtering. The influences of the filter structural parameters, such as coupling coefficient κr, round-trip loss γ1 and additional phase shift Δφ1, etc., on the filtering response are investigated. The result shows that there is a tradeoff between the rectangle shape and extinction ratio. According to the polymer polysilsesquioxane-liquid (PSQ-L) waveguide, a microwave photonic filter with rectangle shape factor of 0.8 and extinction ratio of 32 dB is designed, and the tunable radio frequency single sideband filtering from 8 GHz to 69 GHz can be achieved with the thermal-optic phase shifters.