In this work，white spot defection on phosphating membrane has been researched. When automobile body passes through the pretreatment line of painting workshop，the defection occurs on cold-rolled steel substrate. Through investigations，experiments and SEM analyses，we find that the position of white spot on the phosphating membrane almost without any phosphating crystallizations attached. This phenomenon is owing to the rust corrosion，which is formed during washing process，has been dissolved firstly in the phosphating tank. Then the normal phosphating reaction on the cold-rolled steel substrate has been delayed，which result to the specific position on the substrate almost has no phosphating crystallization. Subsequently，through adding a certain amount of degreasing agent to rinse tank，the phosphating membrane white spot defection on cold-rolled steel has been successfully resolved.