Abstract: Described is the internally-threaded joint failure of the newly-used drill pipe encountered in the field of Pubei 4-11 Well. Macro-analysis of the de fective drill pipe and micro-analysis of the rupture are conducted, and the mate rial used undergoes relevant physiochemical tests, in a bid to identify the major causes of the said failure in terms of structure and load of the drill pipe. B ased on the analyses, corrective are proposed.