The persistent demand for cheaper and high efficient catalysts in chemical synthesis and in novel energy applications, motivated us to study the fundamental interaction involved in water-Cu system. The interaction of Cu and H2O is the precursor of Cu oxidation. Water structure and dissociation kinetics on Cu (110) surface, have been investigated based on first-principles calculations. In both monomer and overlayer configurations, water adsorbs molecularly, with a high tendency for diffusion and/or desorption rather than dissociation on clean surfaces at low temperature. With the increase of the water, the H-bond pattern lowers the dissociation barrier efficiently. During the oxidation of Cu (001) surface, it will form the missing row structure from the c (2x2) structure, with the increase of O2 coverage. We try to find the most stable intermediate state between the two phase transitions, and figure out the mechanism of cu atoms movement during this process.