To address the monitoring of the stress state of prestressed steel strands in prestressed concrete structures, a groove preloading encapsulation quasi-distributed FBG technology is proposed to solve the low survival rate and insufficient monitoring range of FBG. The sensing performance of quasi-distributed FBG steel strands and their monitoring effect on the stress state of concrete structures are investigated via cyclic tension and prestressed RPC-beam loading tests. The results show that the survival rate of the FBG is 100%, the strain sensitivity is 0.001 18-0.001 20 nm/με, the strain transfer rate β≥0.98, the linearity ≤2.096%, the hysteresis ≤1.043%, the repeatability ≤3.615%, and the total uncertainty ≤3.881%. The quasi-distributed FBG steel strand accurately identifies the damage process of the RPC beams. The cracking loads of 45% f_ptk, 65% f_ptk, and 75% f_ptk prestressed RPC beams are 100, 130, and 140 kN, respectively, and the yield loads of the corresponding longitudinal bars are 260, 280, and 300 kN, respectively. The deflection of RPC beams and the strain of steel strands indicate a parabolic distribution, with maximum deflections of 27.691, 20.153, and 14.602 mm, respectively, and maximum strains of 4 163.025 με, 3 715.126 με, and 1 658.487 με, respectively. The quasi-distributed FBG provides ideas for the overall monitoring of prestressed structures.