AbstractTo more accurately describe the mechanical behavior of prestressed steel strands with symmetrical wires breaking in unbonded post-tensioned concrete beam, this paper establishes the equilibrium equation after the bending deformation of the broken wire, taking into consideration bending deformation of the broken wires and the friction between wires and duct. The results derived from this equation fit well with the experimental data. The increase of friction between the center and outer wire and the friction between the broken wire and duct can reduce the recovery length and the strain ratio of the unbroken wire within the recovery length. The increase of axial force before wires breaking will increase the recovery length and the strain ratio of the unbroken wire within the recovery length. The rise in the number of broken wires can reduce the strain the broken wire fully recovers to and recovery length and increase the strain ratio of unbroken wires within the recovery length. In addition, we find that the stress of the unbroken wires near the breaking end becomes greater after symmetrical wires breaking, which is harmful to the structural safety. If there is corrosion in the unbroken wires near the breaking ends, these wires are likely to break immediately following the symmetrically broken wires.