Abstract: The 140 V steel grade production casing pipe bursted during the wellbore pressure test. The causes of the casing pipe burst were analyzed by macromorphology analysis, geometry measurement, mechanical test, metallographic examination, scanning electron microscopy and energy spectrum analysis and so on. The results show that the microstructure, geometric size, mechanical properties and internal pressure strength of the failed casing met the requirements of the standard. The burst mode of the pipe was ductile fracture. The main reason for the burst was that the internal pressure of the pipe exceeded its own pressure bearing capacity, resulting in the overload fracture.