The invention relates to a fuel assembly and a clamping device thereof. The clamping device comprises a clamping assembly, wherein clamping channels allowing fuel rods to penetrate are formed in the clamping assembly; at least two clamping mechanisms for clamping different axial positions of the fuel rods penetrating the clamping channels are arranged on the clamping assembly; each clamping mechanism comprises at least one bulge and at least one elastic arm which are used for clamping the corresponding fuel rod; the bulges and the elastic arms of each clamping mechanism are staggered on the circumferential ring of the corresponding clamping channel, and the bulges and the elastic arms of at least one clamping mechanism are staggered with bulges and elastic arms of the other clamping mechanisms on the circumferential rings of the clamping channels. The bulges and the elastic arms of the different clamping mechanisms are staggered on the circumferential rings, so that the elastic arms and the bulges are stressed on different sides of the fuel rods, when the elastic arms loosen, the positions of the fuel rods are limited by means of staggered arrangement of the bulges, horizontal displacement of the fuel rods during vibration is suppressed effectively, the risk caused by deviation shaking of the fuel rods when the elastic arms fail is reduced, and additional abrasion of the fuel rods caused by lateral clearance is prevented.