Technique of well logging by directional scanning image means scanning the wall of a well according to the given direction,and makes the wall of a well be unfolded to a continuous plane.Common ultrasonic imaging well logging instruments make the strongest magnetic north signal of terrestrial magnetic field as the starting point of scanning trigger signal,which can neither work in the condition of magnetic shielding or magnetic interference,nor ascertain the location of geologic information.However,by taking gyro-positioning technique to locate artificial magnetic field,the ultrasound image produced by measurement processing,where AC(Alternating Current) signal is induced by rotated coils in the artificial magnetic field as the triggering signal for image scanning,we can quickly and accurately ascertain the fault spot and the damage scale and location of well pipes,so as to provide the reliable basis for making maintenance plan.