Based on the operational mode analysis of the aircraft and fighting vibration data, the dynamic load identification technology is investigated in this paper. Firstly, the theory of the ERA method is introduced. Secondly, the dynamic model of the aircraft is put forward. Thirdly, the strategy for implementation is put forward, where the notices are analyzed in detail. Eventually, an example case is studied, where the operational modes are identified based on the telemetry data including the mode frequency and shape. The mode response are then obtained by mode superposition method and mode orthogonal theory, before the dynamic load is derived.