In this article, the Zn_1-xNi_xO nanoparticles with x= 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.08 and 0.1 have been produced by mechanochemical method. To investigate the structural, morphological, optical and magnetic properties of the samples, the X-ray diffraction, field emission scanning electron microscope, UV-visible spectroscopy, photoluminescence and vibrating sample magnetometer have been used. The results of X-ray diffraction revealed that the Zn_1-xNi_xO nanoparticles with x up to x = 0.03 are single-phase and the impurity phase does not appear in the crystal structure of ZnO, but from x = 0.04 the impurity phase appears in this structure. The results of field emissions canning electron microscope showed average particle size of the ZnO increases with Ni doping. The study of UV-visible spectroscopy showed that the optical band gap of the ZnO nanoparticles decreases by Ni doping, which can be due to sp-d exchange interaction between the band electrons and d-electrons of the Ni²⁺ ions. The study of vibrating sample magnetometer of the zinc oxide nanoparticles and Ni-doped samples showed that in the range of magnetic field from zero to about 2000 Oe they are in the ferromagnetic state. In the higher magnetic field (more than 5000 Oe) the
Zn_1-xNi_xO nanoparticles with x = 0, 0.01 are diamagnetic and for x more than 0.01 they show paramagnetic property.