Optical coherence tomography (OCT) has played an important role in biomedical imaging, especially in ocular and cardiovascular imaging. OCT technology has evolved to frequency domain technology from early time-domain technology due to the advantages of high sensitivity and high speed of frequency domain techniques. The swept source OCT is a type of frequency domain OCT. With the increasing requirements for system speed, sensitivity, and functionality in clinical application, swept source OCT is gradually becoming commercially available and widespread in clinical application. In this paper, the principle of swept source OCT was introduced, the advantages of swept source OCT over time domain and spectral domain OCT systems were summarized, and its clinical application in ophthalmology was demonstrated.