The picosecond time-resolved fluorescence spectra are measured for DCM, orysel violet, DODCI and DTDCI in polar solvents. The time-dependent spectral shifts (TDSS) are attributed to the dielectric ralaxation of the solvent surrounding the solute molecule, whose dipole moment undergoes pronounced change upon excitation-The relaxation times obtained from TDSS are in good agreement with those calculated from the continuum cavity model, indicating the applicability of the continuum cavity model for the description of TDSS.