Through selecting suitable base oils and oily agent, antioxidant, extreme-pressure anti-wear additives and rust inhibitors, and other function additives, the cold rolling emulsions of different particle size distribution were prepared by using the oil-water balance system to regulate the emulsion state. The relationship of the emulsion particle size and the extreme pressure and anti-wear properties was investigated on the MS-10A lever-type friction testing machine. The quality of plate surface after cold rolling by the emulsions of different particle size distribution was studied and compared by using the four-high reversing cold rolling mill.Experimental results show that the particle size distribution is related with the stability and lubricity of the emulsions, and in a certain range of volume average diameter, as the particle size of emulsion increases, the anti-wear and friction reducing properties of emulsions are improved, and better surface quality of coldrolled products can be achieved.