Abstract: Causes for the failure of the P110 casing and slip are analyzed by means of macro morphology observation, geometric dimension measurement, mechanical property testing, microstructure analysis and so on.The results show that the main causes for the failure of the casing and the slip are that the casing and hanger are not coaxial, and structure of the slip is not designed reasonably.And the corrosion medium accelerates the failure process.Accordingly, measures for modifying the slip type hanger are put forward, including increasing the slip length, increasing the slip tooth number, per length unit, and changing the through-out circular groove into a convex shoulder type one.