Currently, it is still a great challenge to describe the excited-state dynamics of the hybrid system of molecule-MNPs with large sizes without using the jellium approximation to the MNPs. Here, we thus divide the nanosized tetrahedron into two parts: the tetrahedral cluster Au 20 and the residue, where Au 20 is described by TDDFT and the interaction of the residue to Au 20 @H 2 O is identified by the near field to which Au 20 @H 2 O is subjected. The near field is obtained by the numerical solution of Maxwell's equations using the classical computational electrodynamics finite-difference time-domain (FDTD) technique. With this regard, the interaction of metal-molecule is described at the atomic level and the strong near-field enhancement effect of NPs can also get involved.