1 wt% La-rich RE was added into the alloy of Mg-6Li-1.5Al. The influence of the RE addition on the microstructure and mechanical properties of the alloy and the deformation behavior of this alloy were investigated. The strengthening mechanisms of the alloy were also studied. Results show that the addition of RE can refine the grain and improve the strength and elongation of the alloy. Extrusion and rolling can improve the strength to a large extent. The strengthening mechanisms for this alloy are mainly the refining strengthening and dispersion strengthening.