Clear aligner, covering the whole dentition, is considered to offer more stable anchorage units, which means the whole dentition would act as a strong anchorage except the teeth designed to move. Although we don't expect any movement of the anchorage teeth, it actually happens. It reminds us to pay attention to anchorage problems. In this article we have discussed the anchorage design in clear aligner therapy, compared clear aligner with traditional fixed appliance on anchorage control and provided some clinical strategies of anchorage design in vertical, sagittal and transverse tooth movement.