Abstract: In order to study the effect of Zr element on the microstructure and mechanical properties of Al_0.15MoNbTaTiV refractory high-entropy alloys, Al_0.15MoNbTaTiVZr_x(x=0,0.25,0.5,0.75,1) refractory high entropy alloy with different Zr contents were prepared by vacuum arc smelting. The microstructure and room temperature mechanical properties of Al_0.15MoNbTaTiVZr_x refractory high-entropy alloys were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), universal testing machine and Vickers hardness tester. The results show that the phase structure of Al_0.15MoNbTaTiVZr_x high-entropy alloys is a single BCC phase, and the microstructure morphology is dendritic. The addition of low-density Zr can reduce the density of Al_0.15MoNbTaTiV refractory high-entropy alloys, while improving the strength of the alloys. This is mainly because adding Zr can achieve the grain boundary strengthening by refining the dendritic structure of the alloy. In addition, the presence of Zr exacerbates the enrichment of Ta and Mo elements within the dendrites, and the enrichment of Al, Ti and V between the dendrites. The compositional segregation leads to decreased strengthening effect of Zr. Among the alloys with different Zr contents, Al_0.15MoNbTaTiVZr_0.75 exhibits better plasticity (ε_p=21.082%) and fracture strength (1929.14 MPa) compared to the others.