To investigate the impact of aerodynamic interference effects between large-span dual-deck bridges on their aerodynamic stability, this paper develops a novel aeroelastic-pressure wind tunnel testing system based on the IEEE1588 clock synchronization protocol. This system enables precise synchronous measurement of surface pressure and structural vibration response. Utilizing this innovative synchronized testing platform, we systematically analyzed the specific influences of section shape, structural spacing, and angle of attack on the aerodynamic interference effect in dual-deck bridges. The study reveals that aerodynamic interference significantly intensifies wind-induced vibrations in double-deck bridges, exhibiting more complex nonlinear aerodynamic behavior compared to single-deck bridges. Furthermore, the newly developed measurement system, characterized by its high precision, excellent data synchronization, and strong adaptability, is not only suitable for studying the bidirectional fluid-structure interaction between structural vibrations and airflow but also effectively supports the establishment of nonlinear self-excited force models. This system provides more effective technical support for the aerodynamic elastic research and wind-resistant design of wind-sensitive structures such as tall buildings and long-span bridges.