In order to solve the structural safety problem that may be brought by the long-term full load work of the miter gates of the ship lock in real time, an on-line deformation monitoring method of herringbone gate based on fiber Bragg grating (FBG) sensing technology is proposed. By modeling and simulating the structure of the miter gate, the stress distribution and the arch collapse of the gate body could be accurately understood. According to the force distribution, several fiber Bragg grating tilt sensors were arranged on the miter gate to dynamically monitor the tilt angle of every part of the gate body in real time. The dynamic change of inclination angle was transformed into structural deformation, and the mapping relationship between arch and deformation is established. The results show that the FBG tilt sensor has good repeatability and can accurately reflect the operation process of gate opening and closing. The maximum stress area of the monitored gate body is near the water seal of the bottom pivot of the gate. The maximum camber is less than 0.1° and the maximum deformation is less than 7 mm.