The traditional piling methods of precast concrete (PC) piles are difficult to pass through the hard soil layers and tend to induce severe soil squeezing effects. To address this issue, the technology of a post-planted PC pile with prebored grouting was analyzed. Based on the project of the Hefei?Zongyang section of G3W Dezhou?Shangrao Expressway, the bearing characteristics of post-planted PC piles were researched by the load tests of five piles in two different field test sections. The results show that the bearing capacity of the PC piles can be effectively improved by setting the cement mortar coating layer around the PC piles. The settlement of the pile top under the engineering design load is only about 1.96?3.28 mm. By considering the structural characteristics of the composite pile body, the resistance of the interface between the inner PC pile and the outer cement mortar changes from large at both ends to small in the middle, and the resistance of the interface between the cement mortar and the surrounding soil increases with the depth, which indicates that the cement mortar coating layer can effectively transfer the load of the inner PC pile, enlarge the diameter of the post-planted PC pile, and reinforce the pile body.