Abstract: Abstract: Clear aligner treatment is more and more popular with patients because of its esthetic, comfort, clean and convenience. More and more doctors pay attention to clear aligner because of the three-dimensional computer aided program design and its simplicity in clinical operation. In recent years, with the development of dental digital technology and materials, more widely clinical application, orthodontists' experience has been constantly accumulated, and the indications of clear aligner treatment have been expanding. In addition, clear aligner also have some weakness, such as insufficient control over long-distance tooth movement, differences between actual tooth movement and computer simulation. Based on case selection and treatment plan, this article elaborates the biomechanics, anchorage control, appliance design and risk of clear aligner in extraction cases treatment. It provides a reference for orthodontists to use clear aligner to treat extraction cases well.