Abstract: The method of monitoring the strain of prestressed twist steel cables under construction by means of embedded optical fiber Bragg grating sensor （FBGS） was studied‚and the influence of temperature‚transverse strain and other factors on the effectiveness of measurement results were analyzed．The mechanics behavior of the prestressed twist steel cables in the complicated constructing environment was probed．It shows that if the temperature changes greatly‚the measurement results should be compensated．And applied the non-uniform transverse strains‚FBGS does not meet the Bragg rules and further study should be made．The test results show that the FBGS has the advantages of easy embedment‚strong resistance to magnetism and absolute measurement of the strain‚therefore it is a good sensor for long monitoring of the structural health inside structures． 

Key words: embedded fiber bragg grating sensor, prestressed twist steel cable, strain, long monitoring