Abstract: In this paper, nano-Cu particles with an average size of smaller than 20 nm were dispersed in cold rolling emulsions for steel strip under the effect of ultrasonic. The tribological properties of the cold rolling emulsion doped with nano-Cu were evaluated by using a four-ball machine, and the worn surfaces of the steel balls were observed by using an optical microscope. We also used the JC2000C1 wetting angle tester to research the variation of the emulsion’s wetting performance when Cu particles were applied. Besides, the lubricity of the cold rolling emulsion doped with nano-Cu for steel strip was evaluated on a four-high rolling mill by using the emulsion without nano-Cu for comparison. Results indicated that Cu nano-particles as the additive used in cold rolling emulsion were able to improve the wetting property, friction-reducing, anti-wear, and extreme pressure properties of the base stock significantly. At the same time, Cu nano-particles also showed good lubricity to the cold-rolled steel strips. Namely, the cold-rolled steel strip under the lubrication of the cold rolling emulsion containing nano-Cu has considerably decreased the after-rolling thickness and obtained excellent surface quality as well. Finally, the lubrication mechanism of Cu nano-particles in the emulsion for cold-rolled steel strip was discussed.