Abstract: The emulsion is used as lubricant in the cold rolling of silicon steel, but it often forms emulsion spots on the surface of strip, which affects the surface quality. In this work, SEM, EDS, XPS, XRD and AFM were used to study the formation mechanism of emulsion spots on the surface of silicon steel strip. The results showed that the strip was oxidized to form the line-shape Fe₃O₄ products, which covered the surface of the strip and made the surface rough, resulting in residue of the emulsion. The water in the emulsion evaporated, while the oil in the emulsion remained in the oxidation area to form black emulsion spots. The composition of the emulsion spot on the surface of silicon steel strip is Fe₃O₄ product and oil pollution. According to the formation mechanism of emulsion spot, the formation of emulsion spots can be effectively reduced by controlling the shape of strip and strengthening emulsion management.