In the present paper, nine kinds of alloys with different contents of zinc and zirconium were cast and the influence of zinc and zirconium individually and jointly on the microstructure of the ZK alloys were investigated. The results indicated that the shape and amount of the eutectic were closely related to the content of Zn. With the increase of Zn content, the eutectic was prone to have fish-bone-like shape. When the eutectic grew up to contact with each other, then network eutectic formed; Zr could intensively refine not only the grain size but also the eutectic, but when Zr>0.6%, compound containing Zr or pure Zr granules would appear. That the increase of the Zn must go with the increase of the Zr proved the combined influence of the two alloy elements.