In this work, a novel expression for nonequilibrium free energy is introduced within the framework of the continuum model. A simple and analytical model for the solvent effect of absorption spectrum of an interfacial molecule is deduced. This model overcomes some lacks existing in the previous theoretical treatments. Associated with the experimental data of N,N-diethyl-p-nitroaniline and 4-(2,4,6-triphenylpyridinium)-2,6-diphenylphenoxide, the present model gives reasonable predication of orientational angles for different interfaces.