The influence of the structure of active-phase precursors on the activity of hydrodesulfurization catalysts was studied using an Anderson molybdonickelic heteropoly compound as an example in comparison to conventional ammonium paramolybdate. The effect of stabilizers of mixed ammonium paramolybdate and nickel nitrate solutions on the final properties of catalysts was revealed. The catalysts were synthesized and tested in pulse microcatalytic and flow reactor units. The benefit of the ammonium salt of molybdonickelic heteropoly acid as an active-phase precursor and the effectiveness of stabilization of ammonium paramolybdate and nickel nitrate aqueous solution by tartaric acid-a procedure that considerably enhances the catalytic activity of the test samples-were shown.