Abstract: Tubings fractured at the position of clamp tooth marks on the surface during oil pumping production in one well. Comprehensive inspection and statistical analysis on tubings with clamp tooth marks were carried out, and the generation process of clamp tooth marks and the stress situation of tubings were researched. The results show that:the tubings were severely bitten by sharp pincer teeth before this operation; wall thickness reduction and stress concentration exited in the damaged tubings, resulting in the cracks and fracture of tubings. It was suggested that the hydraulic clamp without teeth marks should be adopted for tubings during makeup, breakout and repairing process.