Abstract: Abstract: Since the advent of clear aligner technique, clear aligners have become an increasingly common addition to patients due to its improved aesthetics and comfort. With the development of aligner materials and the innovation of software design, orthodontists are having a better knowledge of clear aligner technique, and the indication of clear aligners has been greatly enlarged with increasing treatment difficulty. It is necessary for orthodontists to improve their professional ability and master the characteristics of clear aligner technology for a better approval of comfortable, esthetic and effective treatment technology for patients. This article focuses on the principles of tooth extraction treatment in Class II cases, the importance of vertical control and relevant clinical considerations, including the selection of extraction site, the distribution of the extraction space, anchorage control, torque control of anterior teeth, anchorage preparation of posterior tooth, etc., thus providing necessary information for orthodontists to grasp a better understanding of this new technology.