Quasi-zero stiffness (QZS) isolators have been widely studied owing to their superior low-frequency vibration isolation performance. However, the heavy damping in prototypes will lead to no relative motions between the isolated mass and the excitation at low frequencies, thus the vibration isolation is of failure at low frequencies. To address this limitation, compression springs are replaced with tension springs to reduce system damping in the prototype. These tension springs are configured to form both positive and negative stiffness structures arranged in parallel, thereby enabling the design of a QZS isolator utilizing exclusively tension springs. The QZS condition is derived from the static analysis, and the influence of key parameters on QZS features is analyzed. Wide QZS ranges around the static equilibrium position can be achieved. For dynamic analysis, the harmonic balance method is employed to validate the displacement transmissibility results calculated by the incremental harmonic balance method combined with a continuation algorithm. Theoretical predictions calculated by both methods demonstrate close agreement within the effective isolation frequency band. Finally, a prototype had been designed, fabricated and dynamically tested. Meanwhile, a corresponding simulation model was analyzed using ADAMS. Both the tested and simulated displacement transmissibilityexhibit strong consistency with theoretical predictions. The findings demonstrate that the proposed QZS isolator achieves the initial frequency of 1.5 Hz for vibration isolation and the corresponding linear isolator without negative stiffness is 6 Hz. The results verify the superior performance of the vibration isolation of the QZS isolator based on the parallel mechanism of the positive and negative stiffness structures constructed by tension springs.