Abstract: Wear and tear of casing is a predominant problem in deep wells,especially in high temperature and pressure exploration wells.Often it is a contradiction between protection of casing and that of drill pipe.Measures to protect casing were assumed in Yacheng 4 well,such as controlling platform drift,drilling straight hole in surface rock,adopting suitable drilling rig and drill pipe to control well deviation and reducing rate of deviation.The drill pipes were not worn excessively either.Successful protective measures of this well were analyzed and summed up to compare with other wells.It is hoped that these measurements can present some inspiration for drilling this kind of wells.