Abstract: To address the surface quality degradation and damage issues in conventional cutting of 45 steel, a novel wire abrasive flexible contact cutting method was introduced to meet the engineering demand for low-damage material removal. Non-quenched and tempered 45 steel was selected as the object of study. Single-factor controlled experiments were conducted using a single-wire reciprocating electroplated diamond wire saw. Cross-sectional micromorphology, wire roughness and microhardness variation were systematically characterized. Real-time thermal and mechanical data were collected, and fast Fourier transform (FFT) was applied to the cutting force signals to obtain frequency-domain characteristic curves, through which the influence of wire tension on system stability (vibration frequency) was analyzed. The wear mechanism of the saw wire was elucidated based on the evolution of abrasive grains over the service cycle. Wire tension was identified as the dominant factor affecting cutting quality. Under low-damage machining conditions, material removal was dominated by micro-cutting. Ferrite refinement and pearlite lamella distortion and fracture occurred in the cross-section and near-surface layer. The maximum increase in cross-sectional microhardness reached 83.3 HV0.2. FFT analysis revealed that insufficient wire tension reduced machining stability and induced a 165 Hz high-frequency self-excited chatter, which intensified abrasive sliding and ploughing actions and led to increased heat generation. The primary failure modes of the diamond saw wire were abrasive wear, abrasive grain fracture and complete grain detachment. This work elucidates the material removal mechanism, microstructure evolution characteristics, and saw wire wear behavior, and demonstrates the critical influence of wire tension as a core parameter on cutting quality. Low-damage machining of non-quenched and tempered 45 steel is achieved, providing theoretical foundation and process guidance for the precision machining of metallic materials.