The clustering phenomenon on the solid wall during dropwise condensation is analyzed with reflection spectrum. By the theoretical prediction of reflectivity of thin liquid films with different thicknesses on the stainless steel surface, it is ascertained that the reflectivity value is corresponding to the coacervate character of the steam molecular. Furthermore, by analyzing the experimental data of the reflection spectrum during dropwise condensation, presented in the literature, it is obtained that the reflection character and so the coacervate character lies between liquid and steam after the droplet has fallen off during an actual continuous condensation process. And the clustering model is used to analyze the results, which point out that clusters are formed on the blank surface. And it is found that the different microstructures of the solid wall can lead to different deposition rates of the clusters, which presents an effective way to enhance the heat transfer process of condensation by guickening the deposition rate of clusters with the surface modification.