Sulfation is one of important reasons for the failure of lead-acid batteries, therefore, lead sulfate desulfurization and calcination in order to prepare lead oxide with good electrochemical activity has important significance. A method to transform lead sulfate into lead oxide with the reaction of ammonium carbonate and calcination is introduced. At the first, lead carbonate is obtained in a synthesized solution, after filtration, it is calcined at the temperature of 350 ℃, therefore lead oxide with good electrochemical activity could be produced. The prepared sample and ball-milled sample are analyzed by X-Ray powder diffraction, scanning electron microscopy, respectively. The charge and discharge performance test are carried out and result is obtained that the prepared sample has a higher capacity than factory sample. Finally, the calcination temperature for preparation of samples is compared with different temperatures in term of electrical properties, and the best calcination temperature to prepare samples is obtained. In optimum conditions, uniformed and homogeneous structured lead oxide powder with the particle size of 200~300 nm is prepared. The synthesized lead oxide, as positive of lead-acid batteries, shows a good discharge capacity; the capacity value is 120mAh/g at the discharge rate of 0.5C. Finally, the sample after discharge is analyzed by X-Ray powder diffraction.