Background　As the progress in diagnosis of cardiac surgery and in treatment techniques， more and more complicated and senile patients have received surgical treatment， and in accompany， associated complications owing to surgery are increased. Postoperative cognitive dysfunction （POCD） after cardiac surgery is a serious medical problem as its severity harmfulness to the patient. Since no effective treatment has been discovered yet， studies on POCD have been paid much attention in recent years.　Objective　to call for emphasis on the cognitive dysfunction after cardiac surgery， to reducing the painfulness of POCD patients.　Content　Comprehensively reviewed the postoperative cognitive dysfunction after cardiac surgery in terms of the definition， diagnosis and assessment， as well as pathological mechanisms.　Trend　Further studies are needed to discover the pathological mechanism of POCD， and establishment of effective evaluation systems is urgent for an accurate diagnosis.