Abstract: Precursors of nano-NiO were prepared in aqueous solution through liquid-phase deposition with nickel sulfate as raw material，ammonium bicarbonate as precipitator，and Tween-80 as additive. Then NiO powder was prepared by calcining the precursor in muffle furnace. Product samples were characterized by XRD and SEM. Effect of the molar ratio of NiSO4·6H2O/NH4HCO3，reaction time，temperature for thermal treatment and dosage of Tween-80 on NiO yield and particle size were studied systematically. Results showed that under conditions with NiSO4·6H2O/NH4HCO3 of 1∶4，volume ratio of Tween-80/NiSO4 solution 1.25∶100，reaction time of 105 min，and NiO particles with particle size of 38—60 nm were obtained by thermal treatment of the precursor at 500 ℃，the yield could be reached to 79%.