Research conclusions:(1)Comparing with roadbed bearing capacity，circular arc method is more unsafe used to check the embankment stability.(2)The lateral displacement of roadbed will increase sharply when the load on roadbed approaches or exceeds roadbed bearing capacity，and the existing settlement calculation methods are no longer applicable. The application condition of settlement calculation methods is that the requirement of roadbed bearing capacity is met. ( 3)In order to ensure the stability of the embankment and control the settlement of embankment，the roadbed bearing capacity should be checked in the design of subgrade.(4)Conclusions of this paper can provide a theoretical basis for the further improvement of subgrade design method.