The dependence of excitation energies of the solvatochromic dye, 5-dimethylamino-5'-nitro-2,2'-bithiophene (Me2N-2T-NO2) on the solvent polarity is demonstrated by time-dependent density functional theory (TD-DFT) calculations in combination with molecular dynamics (MD) simulations. Three kinds of solvation models, namely, the continuum dielectric model, the discrete approach, and the combined discrete/continuum strategy, are employed to calculate the lowest dipole-allowed excitation energies of Me2N-2T-NO2 in seven solvents with the dielectric constant, epsilon, ranging from 2.23 to 111.00. Our calculations demonstrate the limitations of the continuum dielectric model in predicting the solvatochromic shift of Me2N-2T-NO2 in very polar solvents with epsilon > 35. The accuracy of the explicit solvent model is largely limited by the size of supermolecular cluster. The combined discrete/continuum solvent model gives a satisfactory description of the bathochromic shift of Me2N-2T-NO2 with increasing solvent polarity, in agreement with the experimental observations.