Abstract: It′s recognized that the roughness dimension and distribution on the icing surface influence the flow structure in the boundary layer and thus the heat transfer characteristics is affected further. Therefore, constructing an appropriate roughness model becomes a strong requirement in order to predict the ice shape accurately. In the current work, a local roughness model was developed based on the mechanical analysis of the liquid water on the icing surface. The proposed roughness model is characterized by film, beads and rivulet. The boundaries between film, beads and rivulet are defined according to the experimental observations in references. The set of transient governing equations developed were solved numerically with the finite volume method using a computational fluid dynamics (CFD) code. The mathematical model can be used to analyze the effect of different icing conditions on the roughness and thus the characteristics of the heat transfer in the icing process can be obtained. Numerical results are presented to show the applicability of the developed model and can be helpful to understand the icing mechanism further. In addition, the multi-step ice predicting code developed in this work can be applied in anti/deicing system design directly. The predictions show that the roughness distribution on icing surface is non-uniform, and the maximum roughness is decreasing with temperature decreases. However, during the whole icing process, the maximum roughness performs an increasing trend. The convective heat transfer was enhanced due to the roughness on icing surface.