Accurately obtaining the temperature distribution of the medium in the shutdown pipeline of waxy crude oil has important guiding significance for making maintenance plan and restart plan.The phase transition process of waxy crude oil involves complex problems such as natural convection heat transfer, latent heat release, difficulty in tracing liquid-solid interface. In this paper, the concept and significance of breaking point were proposed. Taking the breaking point and the freezing point as dividing point, and a new zonal partition model was established based on the influence of phase change of crude oil wax crystal on heat transfer mode, with the corresponding governing equations being established for different regions. With the proposed model, the effects of natural convection on heat transfer, latent heat release, location change of condensate reservoir, heat transfer mechanism and other key issues in the process of oil phase transition were analyzed.