In this paper, we introduce a new way to obtain the emission spectrum of
single molecule driven by external field. A virtual probe field is introduced to simulate
the vacuum field, which causes the spontaneous emission phenomena of the excited
single molecule. The statistical properties of the emission photons caused by the virtual
probe field could be used to obtain the emission spectrum of the single molecule
system. The results demonstrate the well-known Mollow triplet splitting phenomenon
as the single molecule is driven by strong external field.The abstract should provide a
brief summary of the main findings of the paper.