Optical coherence tomography (OCT) has been widely used for early detection and evaluation of therapeutic effects for various skin diseases in recent years. With dramatic advantages over traditional pathological diagnostic methods in detection speed and non-invasiveness, OCT has attracted more and more attention of dermatologists for broader applications. In this article, we compared the difference between OCT and other non-invasive imaging technologies applied in dermatology in vivo, and then reviewed the basic principles and classification of OCT systems and its recent applications progress in dermatology.