Recently, we succeeded in realizing ultra acceleration of our tight-binding quantum chemical molecular dynamics (UA-QCMD) simulator, "New- Colors", which is more than 10,000,000 times faster the traditional first-principles molecular dynamics method. It means that a simulation scale of water molecules using UA-QCMD method is easily extended from angstrom scale to nanoscale. It was shown that our New-Colors simulator was effective to perform nanoscale model of water under laser irradiation. This suggests the possibility of the extension of the findings of bond dissociation of water molecules induced by laser irradiation in the electronic level to the macroscopic behavior. Our group also develops a novel multi-level computational chemistry approach for the phase change of water under laser irradiation, by using the kinetic Monte Carlo method.