Abstract: In response to the need for high-quality weldingof NiV alloy targets, the vacuum hot press diffusion welding of NiV alloy and oxygen-free copper without an intermediate layer was investigated at different temperatures under a fixed pressure of 20 MPa and duration of 1 h. Laser confocal microscope, microhardness tester, scanning electron microscope (SEM), X-ray diffractometer (XRD), and electron backscattering diffraction (EBSD) were used to characterize the changes in the microstructure, interfacial element distribution, and mechanical properties before and after the welding. The results show that vacuum hot pressing can realize the direct diffusion welding between NiV alloy and Cu, and with the increase in welding temperature, the mutual diffusion of elements occurs at the interface, and the shear strength and weld weldingrate are improved, reaching 109.59 MPa shear strength and 100% weld weldingrate at 650 °C. The analysis of metallographic, sputtering surface XRD, and EBSD tests on NiV alloys shows that the diffusion welding with weldingparameter at 650 °C has very little effect on the grain size uniformity and crystal structure of NiV alloys, and it does not affect the sputtering requirement of NiV alloy target material.