Concrete expanded-plate piles have significant advantages in the bearing capacity, settlement, and construction period. The added bearing expanded plate is the key reason for their many advantages; moreover, the slope angle (α angle: the maximum diameter of the bearing expanded plate and the angle formed on the plate) of the bearing expanded plate is the main factor to control the longitudinal symmetry. However, the concrete expanded-plate piles in practical engineering do not exist in a rigid body state, and elastic deformation will occur under variable engineering conditions. In addition, the research in this paper mainly focuses on a flexible concrete expanded-plate pile (F-CEP pile). The flexible pile mentioned in this paper refers to the bending deformation of the pile body under horizontal load, which produces large pile top displacement. This study uses the two methods of small-scale half-plane pile model test and finite element simulation analysis of ANSYS, after referring to the equipotential pile test at the actual site. In this paper, the variation law of the displacement curve and the failure law of the soil around the pile under the horizontal force when the α angle changes are analyzed, and the calculation model of the bearing capacity of F-CEP pile under the α angle change is put forward. This research aims to verify the reliability of existing research and provides strong support for the application, promotion, design, and research of F-CEP piles in construction engineering.