A series of hemicyanine dyes, including monomer ([(E)-N-methyl-4-(2-(4-N,N-dimethyl phenyl) ethenyl) pyridinium] iodide; M) and dimers (1,n-Bis [(E)- 4-(2-(4-N,N-dimethyl phenyl) ethenyl) pyridinyl]-alkane dibromide; n = 3, alkane = propane, B3: n = 5, alkane = pentane, 135; n = 12, alkane = dodecane, 1312), are synthesized and their ultrafast fluorescence up-conversion behaviors are studied. The fluorescence decay curves of these dyes can be well fitted by the sum of several exponential decays in the shorter wavelengths and by the sum of the exponential rise's) with decay(s) in the longer wavelengths. The fact that the values of longest lifetime component at longer wavelengths tend to be a constant proves the existence of a "sink" region on the potential energy surface of excited state. This sink region is around the TICT state, by which the nonradiative transition dominates the deactive decay paths of excited state. The time dependent Stokes shift function analysis of these four dye molecules in methanol indicates that the B5's unique "solvation" behavior is different from others. This difference is contributed by the increased difficulty of the TICT formation of 135 originated from its folded conformation. The time dependent Stokes shifts of M, B3, and B12 are due to not only solvation dynamics but also TICT formation. Detailed analysis is presented in the frame of a "two-state three-mode" model.