Abstract: Prestressed concrete pile is a kind of soil displacement pile, and its application is limited because of the squeezing effect. A new construction method called the inner-digging method which can be employed to dig soil while the pile is sinking is developed to solve this problem. It is environmentally friendly and highly efficienct. To test and verify the squeezing effect of inner-digging piles, the deep horizontal displacement and pore water pressure during construction process of soil after different kinds of pile sinking are measured through contrast tests. The squeezing effect rules of a single displacement pile along the horizontal direction and depth direction in soft clay area are studied, and the squeezing effect of the inner-digging piles is compared with that of hammer piles and bored piles. The test results show that the sinking of the hammer piles leads to strong squeezing effect and exhibits notable rules along the horizontal direction and depth, and different degrees of squeezing effect are shown in different horizons of soil. After the sinking of the new developed inner-digging piles, deep horizontal displacement of soil is very low and pore water pressure has little change. A conclusion is drawn that the inner-digging piles lead to little squeezing effect and have little impact on the surrounding environment in construction. Moreover, they will have a good popularization and application value in the future.