The invention discloses a clamping device for riveting assembling of a large thin-walled assembly. The clamping device comprises a mandrel shaft, an angular positioning assembly, a left plugging disc,a right plugging disc, a left pressing plate and a right pressing plate. Peripheral equipment is a to-be-clamped barrel, a left flange and a right flange. The left flange is connected to the left plugging disc through the left pressing plate. The right flange is connected to the right plugging disc through the right pressing plate. The inner side faces of the left plugging disc and the right plugging disc are attached to the two end faces of the barrel. The mandrel shaft penetrates through center holes of the left flange and the right flange to fix the barrel, the left flange and the right flange together. The angular positioning assembly achieves angular positioning between the left flange, the right flange and the barrel by being matched with pin holes in the left flange, the right flange and the barrel. After the angular positioning assembly is disassembled, machining of each rivet hole of an outer ring of the assembly and the mounting seat position is completed, and the double functions of assembling positioning and mechanical machining clamping are achieved. The clamping device can solve the problems that positioning during assembling of the large thin-walled part is not accurate, and the quality uniformity is not high.