Abstract: The double-pipe shell leakage of an oil company's steam assisted gravity drainage(SAGD)injection well occurred during the injection process. The causes of leakage of double-pipe shell were analyzed by means of macro inspection, nondestructive testing, chemical composition analysis, mechanical property test, hardness test, metallographic examination, energy spectrum analysis, flow field simulation and so on. The results show that the leakage of double-pipe shell is mainly caused by fluid erosion, and the structural defects at the pressure sleeve and the vice-tube accelerated the erosion and thinning process.