By studying a cluster model containing Ni region(phase),Ni3AI region (phase) and Ni/Ni3AI region (interface) with a first-principles method,the occupation behavior and the ductility effect of zirconium in a Ni-Ni3AI system were investigated.It is found that zirconium has a stronger segregation tendency to Ni region than to Ni_3Al region.The bond order analyses based on Rice-Wang model and the maximum theoretical shear stress model, however,show that zirconium has different degrees of ductility effect in these three regions,which originates from its different ability to increase the Griffith work of interracial cleavage 2γint and to decrease the maximum theoretical shear stress T_(max).In addition,it is revealed in this paper that the distinct behavior of zirconium from boron to restrain hydrogen-induced embrittlement can be attributed to their different influences on the crystalline and electronic structures in Ni-Ni3AI alloys. By studying a cluster model containing Ni region (phase), Ni3AI region (phase) and Ni / Ni3AI region (interface) with a first-principles method, the occupation behavior and the ductility effect of zirconium in a Ni-Ni3AI system were investigated. It is found that zirconium has a stronger segregation tendency to Ni region than to Ni_3Al region. The bond order analyzes based on Rice-Wang model and the maximum theoretical shear stress model, however, show that zirconium has different degrees of ductility effect in these three regions, which originates from its different ability to increase the Griffith work of interracial cleavage 2γint and to decrease the maximum theoretical shear stress T_ (max) .In addition, it is revealed in this paper that the distinct behavior of zirconium from boron to restrain hydrogen -induced embrittlement can be attributed to their different influences on the crystalline and electronic structures in Ni-Ni3AI alloys.