Since the chemical stability of SiC is extremely high, there is a low efficiency of SiC mirrors for conventional inductively coupled plasma (ICP) processing method. The plasma processing experiment reveals that the increase of plasma radio-frequency can enhance the arc discharge effect between plasma and SiC. The enhancing effect of arc can increase the processing efficiency of SiC, so the arc-enhanced plasma (AEP) processing method was developed. In order to research the formation principle of arc, the voltages of ICP and AEP were measured respectively by using the self-made probe. The conventional and the arc-enhanced methods were employed respectively to conduct linear scanning machining experiment on the sintered silicon carbide (S-SiC), which demonstrates the higher processing efficiency of AEP method.