A high-speed 8-channel fiber Bragg grating (FBG) sensing system is designed to monitor safety of modern ships and applied to measure strain distribution of large thruster structure with 335-Hz maximum natural frequency. All the monitoring points are tested synchronously, and the data acquisition frequency is 1 000 Hz. The strain resolution of the system is 1 με with the measurement range of ±3 300 με. Results from the tests onshore and at sea are discussed together to accomplish prediction of the dynamic data. The max stress of the whole structure is more than 40 MPa. Experimental results are accordant with mechanical theories.