Abstract: To enable real-time monitoring and evaluation of the soil stiffness characteristics, a bender element array system suitable for model testing has been developed. The system is based on a PLC control unit and employs a multi-channel switching architecture to efficiently manage multiple bender element sensors within a single-channel framework. It offers advantages such as low cost, strong anti-interference capability, and ease of development and maintenance. To verify its applicability in complex testing environments, the system was applied to model tests of horizontally loaded single piles in saturated clay. The small-strain shear stiffness of the soil under both monotonic and cyclic loading was obtained, and the reliability of the system’s test results was quantitatively analyzed by comparison with finite element results. The results demonstrate that the system enables stable and accurate monitoring of the spatiotemporal evolution of soil stiffness, delivering an effective testing methodology for investigating the full life-cycle response of pile-soil systems while establishing a technical foundation for the wider implementation of array-based sensing systems in geotechnical model tests.