This paper was based on the pretreatment coating line of automobile phosphating，the key processes of phosphating to zirconizing conversion，including the adaptability between processes，the impact of phosphorus on zirconizing solution，and the impact of zirconizing film on electrophoretic permeability were systematically studied. Basedon the principle of lean design，process design schemes，engineering design schemes，efficient and reliable equipment phosphorus removal schemes，and process debugging schemes wereformulated. The research results and engineering practices of completing the phosphating tozirconizing process upgrade and vertical production transition in one go within 12 days couldserve as a reference for peers in the field.