Abstract: Proceeding from the practical application of civil engineering, an all-grating low-cost distributed sensing system for simultaneous measurement of temperature, strain and pressure based on the optic Bragg grating (FBG) is proposed by using the multiplexing and wavelength abslute coding features of the FBG sensor. A FBG multi-parameter monitoring system for the bridge structure was designed based on continuous wave modulation frequency technology. The address of distributed FBG sensing network was realized by combining optical frequency domain reflectometry (OFDR) with wavelength division multiplexing (WDM), and the content of multiplexing was increased. The experiments show that the system can accurately monitor the internal strain of the important parts of bridges, and provide the precision data for static and dynamic load testing of bridges.