Operational Modal Analysis (OMA) is a kind of modal parameters identification method based on environmental excitation sources. It is an important measure of vibrationbased structural health monitoring. To research certain civil aircrafte’s modal parameters in operation, the vibration responses were gathered by the accelerators on specified structural locations during its taxiing. By using the Frequency and Spatial Domain Decomposition (FSDD) technique, some specific low frequency modal parameters were identified. Then the analytical model were revised based on the OMA results, and all the low frequency modal parameters were computed. Practice indicates that analyzing the aircrafte’s dynamical characteristics under specific conditions by OMA based on FEM method is feasible.