Abstract: There are several shortcomings of conventional staged acid?fracturing technology in horizontal wells drilled in carbonate rocks:The fracturing stage is limited, full?bore of the strings can’t be realized and water searching and plugging can’t be implemented at the late stge of the production. The paper introduces the main tools and its technical principles of staged acid?fracturing in full?bore horizontal wells and gives the detailed demonstration to the key technology of ball?off plugging. A force model has been established for ball sealer where the ball?sealer can be seated and maintained under the forces of the eyehole, and an equation controlling ball?sealer displacement is obtained.Thus a technique is developed for the minimum displacement control. The field application shows that the staged acid?fracturing technology in full?bore of horizontal wells is matured, and the open rate of staged tools is higher, which can well solved the problems of acid?fracturing in multi?layers and the impact of hole shrinkage inside tubing on the follow?up production