The invention relates to a process method for insulating and thermosetting a top shaft of an insulating structure of a hydraulic generator. In the method, twice winding for top shaft insulating and medium-frequency heating by repeatedly using a sensing coil are completed on a field close to medium-frequency sensing equipment. Due to the adoption of the process method, the repeated assembly and disassembly times of a hoisting tool for workpieces and the reciprocating hoisting times are reduced, the workpiece damaging rate is lowered, workpieces are heated locally, and important finish machining surfaces are not influenced. The process method has the advantages of easiness for operating, saving in time and force, optional adjustment of the workpiece size along with shapes, and the like, and is safe and sanitary.