It is of high importance to develop high-efficient chemosensors for explosive nitroaromatics and explore their sensing mechanisms. In this work, the sensing mechanisms of a series of arylene-vinylene terpyridine conjugated fluorescent probes (P1-P4) for TNP have been investigated in depth. The optical discrepancy of P4 is attributed to the different electron excitation distribution caused by the strong intramolecular twist. The rational combination complex has been proposed and further confirmed with Gibbs free energy profile and H-1 NMR analysis. Frontier molecular orbitals (FMOs) analysis demonstrates that photo-induced electron transfer (PET) is the fluorescence quenching mechanism for the TNP detection.