Abstarct: La2-xSrxNiO4 is isostructure to high temperature superconductor La2-xSrxCuO4 system, but instate of superconductivity shows localization of the charge carriers named charge ordering at a temperature TCO which depends on hole concentration. La2-xSrxNiO4 (x ≈ 0.33) nanoparticles were synthesized by the sol–gel method and sintered at different temperatures to study the effects of sintering temperature on structure and size of the particles. The structures of the samples were investigated by X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR) and field emission scanning electron microanalyzer (FESEM). Energy dispersive X-ray spectroscopy (EDX) was used for elemental identification. Rietveld refinement of the X-ray data revealed all samples have K2NiF4 structure with I4/mmm space group. Resistivity (ρ) of the samples was measured by a standard four-point probe method in temperature range of 60–260K. These data indicated that the charge ordering transition temperature is 230K for sample annealed at 1300ºC which has a particle size about 2μm. By decreasing annealed temperature and so reduction of the particle size, reduction of the charge ordering transition temperature was observed. The charge ordering transition temperature is around 130 K for sample annealed at 920ºC with particle size of about 140nm. The resistivity data were fitted with different conduction models to determine the conduction mechanism. The best fits were observed with a variable range hopping (VRH) conduction mode below charge ordering transition temperature and an activated small polaron hopping (SPH) mode above charge ordering transition temperature.