Abstract: Based on two kinds of consolidating theories, the motion equation method (MEM) and the energy method (EM), the back-calculation equations are established separately so that the foundation's deformation modulus could be calculated using the settlement data of hammer pit, which can easily be obtained in monitoring. According to the dynamic compaction experiment of Beijing Garden EXPO Park, the deformation modulus varies with different compacting times. It is shown that the deformation modulus gradually increases with the number of tamping but the growth diminishes at the same time, and the deformation appears to be stable in the end. The initial deformation modulus is 5~8MPa and it rises to 18~22MPa which is 3~4 times of the initial value after the 7th tamping. Besides, the EM method involves a relatively simple calculating process and can be recommended in similar projects.