Based on the classical electrostatics theory, the model of dipole-dipole interaction in the aggregation of rod-like amphiphilic molecules in Langmuir-Blodgett(LB)films has been presented in the paper. The relations between LB films structure and spectral absorption peak were obtained by using this model. For Z-type films, the dependence of molecular aggregation state on the structure parameters, i.e. separation distance a, separation between two adjacent layers d, molecular orientation θ, and layer number g, were studied by applying our model. The theoretical results agree well with experimental data.