As　an　important　it-conjugated　bridge,　(E)-2-styrylthiophene　possesses　excellent　electronic　transport　and　optical　properties,　showing　great　potential　in　nonlinear　optical　(NLO)　applications.　In　order　to　investigate　the　influence　of　different　donor　units　on　(E)-2-styrylthiophene　in　NLO,　we　synthesized　three　thiophene-based　D-it-A　conjugates　with　dicyanoacetylene　as　the　acceptor　and　different　donors　(MS,　PS,　FS)　by　inducing　intramolecular　charge　transfer　(ICT).　Their　third-order　nonlinear　absorption　was　studied　using　Z-scan　experiments　and　transient　absorption　spectroscopy.　Due　to　the　significant　ICT,　MS　exhibited　the　highest　nonlinear　absorption　coefficient　(beta　=　1.5　x　10-9　m　W-1)　and　effective　third　order　refractive　index　(n2　=　-12　x　10-17　m2　W-1).　Taking　the　strongest　performing　MS　molecule　as　an　example,　we　analyzed　four　types　of　conjugated　bridges　through　theoretical　calculations,　which　indicated　that　(E)-2-styrylthiophene　has　the　strongest　dipole　moment　difference　(Delta　mu　=　34.73　D).　Finally,　transient　absorption　(TA)　spectroscopy　revealed　that　the　nonlinear　absorption　of　these　molecules　is　primarily　caused　by　reverse　saturable　absorption　(RSA).