This paper discusses the application of position-sensitive detector (PSD) technology to a real bridge for the purpose of health monitoring. The PSD system consists of two parts: the assembly of PSD targets with mounted LEDs for emitting light spots, and the PSD light-spot capturer for tracking the sensing lights. To verify the performance and reliability of the PSD system, a series of experiments were conducted on an actual bridge with both a dead load and a live load on the superstructure, and an impact load on the substructure. Multiple PSD targets were mounted on the bottom of the girder for the superstructure, and a reference target was mounted on the top of the pier cap, taken as a fixed point. A 400-kN truck was used as the dead load and as the live load, with various speeds. A single target was mounted on the side of the pier cap beam for the substructure, and a 0.6-kN log was used for the impact. A corresponding dynamic response analysis was performed based on a fine-tuned finite element model to provide a reference for the response of the structure. Comparison of the time history and the frequency domain analysis demonstrated that the measured data and analysis result fitted well with one another. The proposed PSD system has shown a high potential of applicability in the practice of bridge health monitoring.