Abstract: The tribological performance of emulsions with or without iron powder was tested by MRS-10A four-ball friction and wear testing machine and MM-W1A vertical universal friction-wear testing machine. The LMS-30 laser diffraction and scattering particle detection technology was applied in analyzing iron particle size in emulsions. The lubricating properties of the emulsions were conducted on a 4-high cold-rolling mill. The results show that the traces of steel ball grinding spot are deeper with a larger diameter using KD-1 emulsion containing iron powder. The average friction factor of KD-1 emulsion is 0.1007, 22.34% higher than that of KD-2 emulsion. The wear loss of the silicon steel surface is 35% higher than KD-2 emulsion. Obvious abrasion wear and plough wear on the silicon steel surface with the KD-1 emulsion are observed. The experimental results indicate that the content of iron powder in emulsion should be less than 150μg/g with the particle size less than 3μm in the high speed cold-rolled process. In addition, the content of iron can be reduced by magnetic filter or skimmers.