An Mg–8Li–2Zn alloy plate was prepared through a two-pass extrusion process, and the high-temperature behavior of the alloy was investigated at 473–593K under the initial strain rate of 1.0×10 −2 –1.0×10 −1 s −1 . The results indicated that the alloy exhibits a significant high strain rate superplasticity with a maximum elongation of 279% under an initial strain rate of 1.0×10 −2 s −1 . The activation energy is 89.4kJ/mol, indicating that the dominant deformation mechanism in the alloy is grain-boundary sliding controlled by grain-boundary diffusion. Cavities nucleate and coalesce during deformation, which is one of the results leading to the fracture of the material.