To explore the effect of cryorolling on the high-temperature mechanical properties of aluminium alloys, AA5083 sheets were rolled at 83, 173, and 298 K, and the rolled sheets were then subjected to high-temperature tensile testing at 748 K. The elongation to failure of the 83 K cryorolled samples reached 150% at a strain rate of 1 × 10−3 s−1, which was higher than those of the 173 K cryorolled samples (92%) and 298 K rolled samples (80%). Under this condition, the strain rate sensitivity coefficient of the 83 K rolled samples was 0.36, which reached the standard of superplasticity. The enhancement of plasticity of the 83 K cryorolled samples was attributed to the finer grains, the smaller second phase, and the subgrains alleviating more stress concentration. The main deformation mechanisms during the high-temperature tensile deformation were grain-boundary sliding and dislocation slip. Compared to the 298 K rolled sample, the grain size of the 83 K cryorolled sample was smaller, which was suitable for the grain-boundary sliding mechanism. In addition, the uniform distribution of high-density dislocations prevented the dislocation slip mechanism but reduced the stress concentration and the nucleation and growth of cavities at high-temperature deformation.