The aim of this research is to prepare leady oxide with high specific area for lead-acid batteries by a new production process. Leady oxide is produced by a cementation reaction in 1.0 wt% HCl solution using a pure aluminum or a magnesium rod as the reductant. Leady oxide prepared in this process is much superior to Barton-pot or ball-mill oxide in terms of physical characteristics. The particle-size distribution of the leady oxide produced by this new process is similar to that of ball-mill oxide. Its acid absorption, however, is much higher because of the different particle shape with respect to ball-mill oxide. Ball-mill oxide is composed of particles of non-uniform plate shape, whereas the new leady oxide is composed of particles of perfect flat (flake) shape. The former oxide has higher specific surface area and greater acid absorption than ball-mill or Barton-pot oxide.