The mechanisms of fiber Bragg grating (FBG) strain sensors and cable tension measurement are analysised, and strain distribution of cable body, connecting tube, and anchorage zone are also analysised, and then a new cable tension measurement method based on FBG strain sensing of anchorage zone is proposed. Based on the stability principle of FBG, the embedded location of FBG is studied. Scale model experiments are carried out, and the FBG is embedded in the geometrical center of three steel wires to ensure the work stability of FBG. Experimental results show that the measured strain of anchoring region is only 62% of that of measured strain outside, and the central wavelength of the FBG in anchorage zone has a good linear relationship with the tension. The correctness of the theory and feasibility of the cable force measurement method are proved.