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Few studies of cryogenic treatment were focused on nonferrous alloys, such as magnesium alloy. In this work, the effect of cryogenic treatment (77 K) before extrusion on microstructure and mechanical properties of ZK60 alloy was investigated. The results showed that many fine G.P. zones were formed during the cryogenic treatment and then grew to short fine β1′{\beta }_{1}^{^{\prime} } precipitates when heating before extrusion. These precipitates pinned dynamic recrystallized grain boundaries in the subsequent extrusion, resulting in fine gains and dispersed spherical precipitates. By the cryogenic treatment before extrusion, the extruded ZK60 alloy showed good tensile strength and elongation balance. Especially, elongation was improved by 29%.