Abstract: The objective of this study is to develop a novel and effective nano-NiO catalyst to be used in biomass gasification for tar removal. For this purpose, in this study, nanocrystalline NiO particles were successfully prepared by the homogeneous precipitation method, and different approaches including thermogravimetric analysis, Fourier transforms infrared spectrometry, X-ray diffraction, BET surface area measurement and transmission electron microscopy were used to characterize the nano-NiO particles and its precursors. Meanwhile, the process of the nanocrystalline NiO particles derived from precursors was thoroughly analyzed. The analysis results indicated that the as-synthesized precursor was hydrated nickelbasic carbonates and its formula was identified as NiCO3 · 2Ni(OH)2 · nH2O, and it can completely transform into nanocrystalline NiO particles below 360℃ under the air atmosphere. Furthermore, the effect of calcination conditions on the crystalline size of nanocrystalline NiO are very crucial. The prepared NiO nanoparticles were found spherical in shape, could be well dispersed and demonstrated weak agglomeration. They had generally high purity and a fine crystal phase of cubic syngony with a mean size of about 7.5nm and specific surface area of 187.98 m2/g, the high specific surface areas of the NiO nanoparticles suggested its possibility of application as efficient catalytic materials.