To examine the monitoring performance of optical frequency domain reflectometry (OFDR) and ultra-weak fiber Bragg grating (UWFBG) technologies in the bridge steel structure, this study focuses on the bending measurement experiments of H-shaped steel beam. Four optical fibers are arranged along the full length of the steel beam and distributed strain measurement investigations are performed under heavy and light load conditions for the four-point loaded bending deformation of the steel beam. The findings reveal that both OFDR and UWFBG technologies indicate remarkable monitoring performance in the distributed strain measurement of the steel beam. Compared with the findings of the strain gage, the average measurement errors of the OFDR technology and UWFBG technology under heavy load conditions are within 3 με and 2 με and under light load conditions are within 2 με and 1 με, respectively. The test findings for the 0.9 mm tight-buffered fiber and the bare fiber are similar, demonstrating that the tight-buffered fiber does not minimize the fiber's strain transmissibility. In addition, the spatial resolution of UWFBG measurement findings can be enhanced through experimental design, and the degree of improvement depends on the grating density of the laid fibers and relative grating spacing between adjacent fibers.