© 2020This study presents the synthesis of magnetite nanoparticles by hydrothermal methods and DFT (Density Functional Theory) analysis of Fe3O4 cluster as its smallest representative unit. OPBE functional with the basis set of 6–311+G(d) has been used to study Fe3O4 cluster with the spin state of M = 5. The quantities for optimized geometry, spin distribution, charge distribution, dipole moment, and frontier orbitals have been obtained and used to make theoretical analysis. Fourier transform infrared spectroscopy for characterizing structures was used and also size and the structure of nanoparticles obtained was studied by X-ray diffraction analysis. In addition, morphology of surface was also studied.