To explore an efficient polishing method for ultra-hard brittle silicon carbide materials, an ultrasonic-electrochemical mechanical polishing experiment was performed on the SiC specimens by controlling variable method. The SiC specimens were polished by cast iron polishing plate, polyurethane polishing plate and semi-fixed abrasive polishing plate in three kinds of polishing liquids, i.e. tap water, KOH solution and Fenton reaction solution respectively, and the optimized polishing process parameters based on the material removal rate and surface quality of SiC specimen were obtained. The results show that the material removal rate is high when using cast iron polishing plate, but the surface quality is poor. The surface quality is best when using semi-fixed abrasive polishing plate, but the material removal rate is low. The Fenton solution has the best effect on improving the material removal rate. When the voltage between specimen and polishing plate is +10 V, the material removal rate is the highest, which is raised by 55.1% than that without voltage. When the ultrasonic vibration of the specimen retaining ring was applied, the material removal rate was increased by 91.7% compared with that of non-ultrasound. The ultrasonic vibration plays a major role in the polishing of SiC specimen.