The current studies have shown that plaque rupture of a vulnerable plaque is the main cause of Acute Coronary Syndrome (ACS). The important point is to find and treat a vulnerable plaque to prevent the acute event. Many imaging modalities have been introduced to identify thin-capped fibroatheroma (TFCA). But the morphology and the mechanism of rupture of vulnerable plaques are still the clinical problems. Intravascular Optical Coherent Tomography (IVOCT) is an examine method based on cardiac catheter. It uses near-infrared light, for up to 10 microns high-resolution images, thus to obtain images and tissue characterization on a microscopic scale. With the development of a new generation of Frequency-Domain OCT (FD-OCT), this technology has played a positive role in the study of TCFA. Our main objective is to review the studies of TCFA with OCT. Development of IVOCT might provide new insights into the diagnosis and treatment of coronary heart disease.