In this work,we thoroughly study newly synthesized Photoinduced electron Transfer (PeT)-based two-photon Nitric oxide (NO) fluorescent probes (Q and L) [1,2].Response theory is used to investigate one-photon absorption (OPA) and two-photon absorption (TPA) as well as emission properties of Q(L) in the absence and presence of NO using density functional theory (DFT) method in combination with polarizable continuum model (PCM).Evolution on optical properties of Q(L),including enhancement of fluorescent intensity and increase of TPA cross section upon combining with NO,are specially emphasized.