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For non-oriented cold-rolled silicon steel lubricated with oil-in-water (O/W) emulsion, the typical white-stripe defects can always be found on the rolled strip surface. The white-stripe defects are parallel to the rolling direction. In this paper, an experimental investigation and mechanical analysis were carried out to study the white-stripe defect formation during cold strip rolling using atomic force microscopy (AFM) and scanning electron-microscopy (SEM). The emulsion lubricating properties and surface topography of wear scars are discussed. It is considered that the poor lubricating properties of the emulsion are a key factor for surface defect formation on the rolled strip surface. The surface roughness Ra of the white-stripe area is 31.2% larger than that of the normal area. The results show that when the tribological properties of commercial emulsion are poor; it will lead to generate surface defects on the rolled non-oriented silicon steel surface. Furthermore, emulsions were embedded into the surface defects of the rolled strip. When the emulsion residue agglomerates together, white-stripe defects appear on the rolled strip surface. [ABSTRACT FROM AUTHOR]