Mg–5Li–3Al–2Zn– xSn ( x = 0.5, 1.0, 1.5, 2.0) alloys were designed and prepared using vacuum melting furnace. The microstructure and mechanical properties were tested after extrusion to reveal the effects of Sn on the alloys. The results show that, the deformed alloy is composed of α phase and Mg 2Sn. With the addition of Sn, the grain size of deformed alloy is refined. When the content of Sn is 1.0%, the grain size of alloy is the finest. The addition of Sn also improves the strength of the alloys due to the formation of Mg 2Sn phase and refining effect. When the content of Sn is 1.0%, the strength is the highest (306.95 MPa).