The purpose of this study was to compare the flow abnormality based on 4D Flow MRI data with the PG measured by Doppler ultrasound. we enrolled 9 patients who underwent echocardiography followed by 4D Flow MRI. Helical grade of HOCM group was higher than that of HNCM group (2.33±0.47 vs. 1.33±0.47, p=0.032). There was no significant difference between HG and each characteristic of HCM (PG, septal thickness, septum/free wall ratio and the presence of SAM). 4D Flow MRI can visualize abnormal helical flow of ascending aorta in patients with hypertrophic obstructive cardiomyopathy.