The invention provides a method for processing rotary parts by using water electrode and air plasmas and belongs to the technical field of processing rotary parts of silicon-based materials such as silicon carbide and fused quartz by using plasmas. The method provided by the invention is used for solving the problems of uneven discharge, thermal deformation of workpieces and the like. The method comprises the following steps of: step 1, connecting the upper end face of a rotary forming electrode to a rotating shaft, wherein the rotary forming electrode is circular and outwards convex; step 2, dipping the outer surface of the part to be processed in electrolyte aqueous solution in a water tank; step 3, closing the rotary forming electrode to the surface to be processed of the part to be processed; step 4, preheating a radio-frequency power source and mixing a plasma gas source; step 5, putting the rotary forming electrode in rotary motion and starting the radio-frequency power source; step 6, controlling the movement locus of the rotary forming electrode and staying time on the surface of the part; and step 7, taking out the part to be processed. With the application of the water electrode in the method provided by the invention, the electrode is fitted with the surface of the workpiece without clearance and discharges evenly, and as a result, the processing accuracy is guaranteed and the processing stability is improved.