The precipitation microstructure and mechanical properties of as-cast 3104 alloys with different Zr additions was investigated. The results showed that the grain size of alloy decreases with the increase of Zr content, and it has the smallest grain (20μm) when the mass fraction of Zr (Zr wt%) was greater than or equal to 0.25%. Meanwhile, the grain shape changes from feathery to equiaxed. Furthermore, Zr can improve the distribution of Si and Mn elements in the alloy by forming Si phase and other intermetallic compounds. Vickers hardness analysis showed that the addition of Zr will reduce the hardness of Al-Mn-Fe 3104 alloy. Moreover, according to the results of tensile test, tensile strength and the elongation of the cast alloy are increase with Zr content increase until Zr wt% was 0.25%. The proper content of Zr plays a role of pinning dislocation and preventing slip, which improves strength and toughness of the alloys.