Regional cerebral oxygen saturation cerebral oxygen saturation(rScO2) monitoring by using near-infrared spectroscopy(NIRS) is a simple, sensitive, continuous and noninvasive method, which can detect the change in oxygen supply and demand. It has already draw attentions and applications during perioperative in recent years. The technique was firstly used in cardiac surgery, thereafter some studies found thoracic surgery which mostly used one-lung ventilation also was necessary to monitor rScO2. A series of studies confirmed there were correlations among perioperative adverse events and rScO2. In this paper, we reviewed the basic principle of rScO2, summarized the applications of rScO2 in cardiac and thoracic surgery, discussed the existing problems.