In order to understand the capacity of water vapor to transport copper and its mechanism,using the solubility method, the solubility of copper in undersaturated water vapor was investigated experimentally at temperatures from 310 ℃ to 350 ℃ and pressures from 42 × 105 to 100 × 105 Pa. Results of these experiments show that the presence of water vapor increases the concentration of Cu in the gus. At a constant temperature, the solubility of copper increases with increasing water vapor pressure.Copper may exist as hydrated gaseous particles in the vapor phase, and the dissolution process can be denumber decreases with increasing temperature, varying from ～6 at 310 ℃, to ～5 at 330 ℃, and ～4at 350 ℃. The results show that interactions between gas-solvent H2O and copper will significantly enhance the dissolution and transport capacity of copper in the gas phase.