To unveil the possibility of water fragmentation, we perform a calculation of absorption spectra of Au 20 @H 2 O with the varied laser intensity. Figure in SI shows the calculated results. We observe that as the field intensity continuously increases, the intensities of high-energy absorption bands with excitation energies ≥ 2.9 eV decrease and their peak locations blue-shift while the intensities of low-energy absorption bands continuingly increase. These phenomena manifest that the intensive laser fields couple with the system Au 20 @H 2 O nonlinearly. The decrease of the high-energy absorption and the integrated energy shift are attributed to the absorption saturation and the field dressing during the excitation. The appearing and continuing increasing intensity of low-energy bands confirms that the multiphoton absorption occurs. This nonlinear coupling between the system and laser field definitely affects the dynamics of water splitting and may lead to the water fragmentation.