Abstract: The relations between the grain size and the mechanical properties of high aluminum cast ZA-alloys (w(Al) =28.4%) with/without B, Ti and Zr were statistically analyzed. It is showed that there isn't any notable interrelationship between the grain size and the ductility of the alloy. The microstructure, X-ray diffraction and microprobe analyses for the fracture surfaces of the alloy were carried out. The results indicated that the remarkable increase of the ductility of as-cast high aluminum ZA alloy modified with B, Ti and Zr is attributed to the elimination of inter-dendrite porosity and the lessening of dendritic segregation of preeutectic aluminum-rich phase.