Ultra-high performance lightweight concrete (UHPLC) is a kind of lightweight cement-based material with properties of high tension and compression ratio and tensile strain-hardening. To investigate the collaborative tension mechanism between UHPLC and steel before the yield point of the steel, a self-designed tensile loading system was used to conduct cyclic tensile loading. The adopted UHPLC has a density of 1 789 kg/m³, compressive strength of 63.1 MPa, ultimate tensile strain of 2.4×10^-3-2.8×10^-3, and ultimate tensile strength of 6.9-7.8 MPa. Four cyclic loading conditions were applied, i.e., tensile strains were 2.0×10^-4, 5.0×10^-4, 1.0×10^-3, and 1.5×10^-3, respectively. Test results show that the envelope curves of the cyclic tensile stress-strain curves were in high consistency with the direct tensile stress-strain curves. The residual strain, stiffness of loading, and stiffness of unloading that derived from the cyclic loading test reflected the debonding situation of the fibre at bridged micro-cracks. The larger the residual strain was, the longer the debonding length of the fibre was, which resulted in the reduction of the loading and unloading stiffness. When the cumulated tensile strain under the cyclic tensile loading was smaller than the ultimate tensile strain, the multiple cyclic loading led to a cyclic tensile action on the debonding part of the fibre. The degradation rate of the loading stiffness and the cumulated residual strain followed a power function with a fitting degree of 0.99. The stiffness of the UHPLC under cyclic tensile loading was decided by the effective length of the fibre (the debonding part) under tensile loading, which could be characterized by the cumulated residual strain.