In this paper, a novel polishing method using magnetorheological (MR) fluids is presented to improve surface quality and resulting high frequency performance of the electroplated three dimensional geometries. The MR fluids are utilized to efficiently polish uneven and imperfect conductor surfaces due to the widely used electroplating processes. For performance comparison, two 50 Ω CPW lines and λ/2 open-end resonators on glass substrate are fabricated to validate the characteristics of the proposed polishing scheme. From the measurement, it is revealed that the polished CPW lines using MR fluids show much lower attenuation constants up to a maximum of 0.3-0.54 dB/cm than unpolished CPW lines. Moreover, loaded Q factors of λ/2 open-end resonators are dramatically improved when employing the MR fluids polishing scheme.