Abstract: In order to make full use of multiplexing capability of fiber Bragg Grating(FBG) sensing system while the optical signal of each sensor along sensing optical can be detected effectively and to provide basis for sensor design and manufacture, based on FBG sensing principle, aiming at the system integration and optimization of multiplexing capability of the sensing system, the design method of wavelength division multiplexing and the design principle as well as criteria of node sensor structure and sensitivity were proposed and applied to the optical monitoring system of a real engineering.During working of the sensing system, reliable monitoring data about the engineering was obtained.Results show that the difference between monitoring results measured by FBG sensors and those from point-type electric instruments is about 6%, further indicating that there is no sensor signal crosstalk near the optical fiber sensor, which provides a useful reference for the engineering construction and safety maintenance.