The invention relates to the preparation of cobalt powder, in particular to a method of synthesizing low-oxygen superfine cobalt powder. The method includes the steps of 1, controlling cobalt salt which is soluble and ammonium bicarbonate or alkali to react at room temperature according to a certain ratio, under the PH value of 6 to 7; 2, stopping addition of the cobalt salt, continuing to add the ammonium bicarbonate to adjust the PH value to above 7.1, performing slow heating to 45 to 60 DEG C, and allowing ageing reaction to form cobalt precursor; 3, subjecting the cobalt precursor to hydrogen reduction under certain conditions, subjecting reduced cobalt powder to cooling and passivation in the protective atmosphere so as to form a dense protective film on the surface of the cobalt powder and to reduce contact area of the cobalt powder with air, and performing jet crushing, mixing, screening and vacuum packaging in the protective atmosphere to obtain low-oxygen superfine cobalt powder. The method has the advantages that particle size and density of the cobalt powder can be controlled and the low-oxygen cobalt powder is convenient to store.