Abstract: A crack is found with the BG27CrMoV trenchless geological drill pipe.Briefly analyzed are the main aspects of the said failure drill pipe, including the operation conditions, the chemical composition, the metallographic structure, the mechanical properties, and the composition of the corrosion products, etc.It is regarded via the analysis that the crack has nothing to do with the chemical composition, the metallographic structure and the mechanical properties of the failure drill pipe which are all normal.The analysis of the operation conditions and the corrosion products of the drill pipe reveals the existence of FeS in the later, which leads to such a conclusion that the crack of the failure drill pipe is caused by the SCC effect.