The invention discloses a system for observing and simulating a wind-wave-flow coupling field for a sea-crossing bridge, and the system comprises a wind observation system, a wave flow observation system, a tide level observation system, a data collection and storage system, and a wind-wave-flow coupling field numerical analysis system. The wind observation system comprises a plurality of wind observation stations, and the wind observation stations are located on the lands of two shores for gradient wind observation. The wave flow observation system comprises a plurality of wave flow observation stations, and the wave flow observation stations are located in nearby water areas for continuous observation of wave surfaces and layered flowing speeds. The tide level observation system comprises a plurality of tide level observation stations, and the tide level observation stations are located in water areas which are located at the place of the bridge and nearby the shores. The observation data of the spatial correlation among wind, wave, ocean current and tide level and the time synchronization and continuous observation data are stored in the data collection and storage system. Based on the above observation data, the wind-wave-flow coupling field numerical analysis system builds a wind-wave-flow coupling field numerical simulation model. The wind-wave-flow coupling field characteristic parameters which are spatially correlated and synchronous in time and act on the bridge are analyzed through combining with historical observation data after verification and correction.