Abstract: Macroscopic and microscopic analyses were conducted for 9 typical bursting incidents in hydraulic tests of seamless pipe production. The analysis results show that bursting in the hydraulic tests is always related to some defects existing in some parts of pipes. Defects in continuous casting billets include surface cracks, surface slag and surface carburetion, surface copper infiltration, central segregation and internal inclusion segregation, etc. Defects existing in hot rolled pipes include surface scratches, ununiformity or reduction of wall thickness, and so on. Defects caused by tube processing include surface quench cracks, abnormal microstructure, low yield strength and low precision of thread machining of pipe ends. Suggestions for improvements are also provided according to the analysis results