Abstract: The dynamic compaction treatment method of foundation with interbedded liquefiable soil and soft soil is studied for expressway in this paper. The formula of treatment depth for dynamic compaction is presented according to the pseudostatic mechanics method. It is of obvious meaning of soil mechanics compared with Mendard’s formula. The results calculated by the formula of treatment depth for dynamic compaction are in agreement with the measured results. Simultaneously, the treatment method of low energy dynamic compaction is put forward based on the measured results for the foundation interbedded with liquefiable soil and soft soil. These methods are of practical value for foundation treatment of the expressway.