In recent years, the highway construction has developed rapidly all over the world, but many highways have uneven pavement after a period of use. The collapse and subsidence are the major influence factors. The same situation also occurred during the subgrade construction process of the railway. The subgrade is an important part of railway engineering.It is the basis of bearing the weight of track structure and trainload. Also, it is the most unstable and weakest link in railway line engineering. The excessive sinking of subgrade will cause many subgrade diseases, increase maintenance cost and affects traffic safety.