Ascending aortic dissection is a life-threatening disease. Once diagnosed, patients should be immediately managed for appropriate diagnosis and treatment. The golden standard for diagnosis of ascending aortic dissection is computer tomography (CT) aortic full-length imaging. However, this patient underwent preoperative tests of CT aortic full-length imaging and routine transthoracic ultrasonography. But diagnosis of ascending aortic dissection was ignored. The root of ascending aortic dissection was found by transesophageal echocardiography during operation. The aortic dissection involved the opening of the right coronary artery the position of aortic perfusing intubation and surgical plan were adjusted in time. The prognosis of the patient was good. This case provided experiences in avoiding missed diagnosis of aortic dissection in patients with ascending aortic aneurysm.