Left ventricular diverticulum（LVD） represents an rare congenital anomaly. Subaortic diverticulum (SD) is a special type of LVD. It is consisting of a localized outpouching from the free wall of the left ventricular outflow tract and can cause aortic regurgitant，with a male to female ratio of 16:1. SD should be distinguished from aortic dissection in addition to aortic sinus aneurysm. We report a female case of subvalvular diverticulum with aortic dysplasia misdiagnosed as a major artery dissection by bedside echocardiography. The patient had mild symptoms and underwent diverticular repair and aortic valve replacement.