Abstract: The fracture failure of the drill-string is badly impacted on the problem that bite-mark on the surface of drill-string caused by slip, a system method of evaluating the impact of slip bite-mark on the fracture failure of the drill-string is established. The damage model of drill-string is established based on the stress analysis of the drill-string hoisted by the slip and the elasticity and plasticity. The evaluation parameters of the fracture failure caused by the slip is obtained by analyzing the theory of fracture mechanics, and the axial load, the fracture toughness and the defect size are closely linked up to evaluate the serviceability of the drill-string. The failure evaluation curves of the drill-string with slip bite-mark is appropriated for the oil fields，according to the theoretical analysis. The three-level evaluation method for drill-string with cracks is presented, and an effective reference is provide to the oil fields security operation.

Key words: Damage model, Drill-string, Fracture failure, Serviceability, Slip bite-mark, Three-levels evaluation