The new traffic distribution function of the city needs to be implemented by connecting the external expressway and the interchange. The high density of interchanges of the near-city ring expressway section and the small clear distance between the adjacent interchanges make it difficult to establish new interchanges. To meet the demands of the new interchange functions, reconstruction and expansion of existing interchanges is used. In other words, it can be carried out by converting the existing interchanges and adding ramps that meet the requirements of expansion functions. This paper discusses the precondition and primary considerations for the scheme formulation and establishment of the interchange conversion and expansion plan. We also describe the specific design process and the reference regulations in details. We expect this project can provide a useful reference for the interchange reconstruction and expansion under similar construction conditions in the future.