In the road engineering, conventional subgrade design is mainly concerned with the uneven settlement and post-construction settlement of the subgrade; in the case of obviously poor site conditions, such as silt or silt soft soil and other soft soil foundations, it is directly considered to use replacement gravel for compaction or foundation treatment for reinforcement. For general clay or silty soil sites, after clearing the existing ground, we fill the roadbed and check the stability of the filled roadbed slope, but the checking of the bearing capacity of the existing ground is often ignored. And there are no relevant calculation or design requirements on the bearing capacity of road foundations in the current code. Combining actual engineering cases, based on the theory of the bearing capacity of Prandtl L and Terzaghi K, this paper analyzes the bearing capacity of the subgrade under the fill road and the design check calculation method, so as to provide a reference for similar engineering design in the future.