Clamping device and clamping method for machining inner surface of high-gradient thin-wall element

The invention relates to a clamping device and method for machining the inner surface of a high-gradient thin-wall element. The clamping device comprises a mounting disc, an element supporting disc, a plurality of supporting plates, a fixing ring, a plurality of puller bolts and a plurality of longitudinal pressing pieces, and a plurality of positioning adjusting holes are formed in the mounting disc; the element supporting disc is fixed on the upper end surface of the mounting disc and is provided with an arc-shaped surface at the top; a first threaded hole is formed in the supporting plate; the fixing ring and the mounting disc are coaxially arranged and fixed at the top end of the supporting plate; the multiple supporting plates, the element supporting disc and the fixing ring form a clamping space used for clamping the high-gradient thin-wall element. The puller bolt is correspondingly screwed on the first threaded hole, and the screw rod end of the puller bolt can be propped against the outer wall of the