The influence of starting materials on the formation of BaPbO3 is studied. The reaction kinetics of perovskite BaPbO3 phase formation depends greatly on the phase of lead oxide raw materials. Kinetics of BaPbO3 formation is analyzed by the Johnson-Mehl-Avrami model. The experimental results reveals that the reaction of BaCO3-PbO2 raw materials has a reaction order of n = 5/2, and the reaction is controlled by diffusion. On the other hand, in the case of BaCO3-PbO system, the reaction order n is equal to 1. The formation is controlled by the interface reaction. In the final stage of both systems, the reaction orders are the same of about 0.5. The phases left in the final stage are BaPbO3 and BaCO3.