In recent years, some Ni and Al containing ceramics have drawn interests in the development of industrial catalyst and anode in SOFC. Nickel Aluminate (NiAl 2 O 4 ), is such materials which introduce previously as a catalyst and recently as a anode for SOFC. Furthermore, nickel aluminate nanopowder has shown better catalytic behavior in comparison with micronize nickel aluminate. The objective of present research was to provide and characterize of nickel aluminate nanocrystalline powder by mechanical activation. In this study, aluminum, alumina, nickel oxide, nickel carbonate, magnesium carbonate, ammonium fluoride and ammonium chloride powders were used as initials materials. Ammonium fluoride and ammonium chloride powders were utilize as the speedup reagent of the process. The influence of different factors such as mechanical activation time, heat treatment temperature and time, using calcined initial materials, ammonium fluoride and ammonium chloride powders on the phase structure and crystallite size of prepared powders was investigated. Various techniques were employed to evaluate and characterize the produced product. To evaluate the phase structure and support of appearance of desirable phases in obtained composition, X-ray diffraction (XRD) technique was used. Thermal gravimetry analysis (TGA) was used to evaluate the thermal behavior of produced product. To investigate the morphology and particle size distribution of starting and obtained powders, Scanning electron microscopy (SEM) was employed. Also, morphology and crystallite size nanocrystalline nickel aluminate powders were characterized by Transition electron microscopy (TEM). Energy dispersive x-ray (EDX) was used to investigate the solution while mechanical activation. Considering performed experiments and thermodynamic evaluation of the system, some mechanisms was proposed to explain reactions which were done in the procedure of producing nanocrystalline nickel aluminate powder as a hypothesis. nanocrystalline nickel aluminate powder could be provided by 5 h mechanical activation of aluminum and nickel carbonate after post annealing at 1300 o C for 1 hour with crystallite size of 18 nm. Results showed that the presence of fluorine ions increased the reaction rate of single phase nanocrystalline nickel aluminate powder after 3 h mechanical activation and 1 h heat treatment at 1200 o C. But the presence of colorine ions had vice versa effect. In another route, nanostructure nickel aluminate powder with 53 nm crystallite size obtained by 5 h mechanical activation alumina and nickel carbonate powders and then 1 h heat treatment at 1300 o C. Key words Nickel Aluminate, Nanostructure materials, Mechanical activation, Heat treatment, Spinel.