Objective To study the blood flow dynamics changes and clinical value of before and after the pulmonary arterial valve with PC-MRI. Methods 33 healthy youth volunteers were enrolled. SiemensSomatonAera 1.5T magnetic resonance system and Syngo Argus flow measurement solfware were used in this study. The peak and average velocity and the average flow per minute before and after the pulmonary arterial valve were measured by perpendicular to the point of 1.5cm before and after the pulmonary valve with through-plane PC-MRI. The main pulmonary arterial mean pressure(mPAP) with Argiento P formula (mPAPA) and Bernolli equation (mPAPB) were calculated and compared separately. Rusults The peak and average velocity before and after the valve had no significant differences(P＞0.05) and there was a statistical differences between that of average flow per minute(P＜0.05). According to the Argiento P formula and Bernoulli equation, the mean pulmonary arterial pressure have diffencese(P=0.000). Conclusion The hemodynamics before and after the pulmonary valve can be measured accurately by PC-MRI, which is a valuable method for assessing the pulmonary blood flow dynamics changes, especially for the diagnosis and evaluation of the Idiopathic pulmonary hypertension.