Abstarct: In this thesis, NiMn2O4 nano powders were syntesies by sol-gel method and then were annealed at 700°C, 800°C, 900°C and 1000°C for 6 hours. The structural properties of the samples were analyzed using a x-ray diffraction diffractometer, a scanning electron microscope, a Fourier-transform infrared Spectrometer and a Energy-dispersive X-ray spectrometer and the magnetic property of the samples was analyzed using a vibrating-sample magnetometer . The results of the XRD analysis show the samples have a cubic spinel structure of NiMn2O4. The FTIR analysis confirms the existence of the bond between nickel and manganese elements with oxygen and forming the structure of NiMn2O4. FE-SEM images and surface morphology studies show the annealed sample at 800 ° C has uniform and smaller grain sizes. EDX analysis confirms the presence of the main elements of nickel, manganese and oxygen in the samples. Finally, the results of the VSM analysis indicates the paramagnetic / antiferromagnetic phase for annealed samples at 700°C and 900°C and a weak ferromagnetic behavior for annealed sample at 800°C at room temperature.