Objective：To analyze the hemodynamics before and after endovascular and conservative treatment for spontaneous isolated superior mesenteric artery dissection（SISMAD），and to provide hemodynamic evidence for effectiveness of the two therapies. Methods：A retrospective analysis was performed on 30 patients with type Ⅰ and type Ⅱ SISMAD from November 2015 to March 2018. The pa－tients were divided into endovascular treatment group（12 patients） and conservative treatment group（18 patients）. Based on imaging data from computed tomography angiography，a computational fluid dynamics analysis was conducted to evaluate hemodynamic changes after treatment in the two groups of patients. Results：Both groups of patients received safe and effective treatment. Hemody－namic results showed low blood flow velocity，high wall pressure，and low wall shear stress（WSS） in the dissected segment of the su－perior mesenteric artery（SMA） on admission，with the lowest WSS in the false lumen. After endovascular treatment，blood flow in the SMA returned to a stable level，the wall pressure decreased，and the WSS increased to a stable state. During the conservative treatment，with false lumen thrombosed and absorbed，the true lumen was remodeled，blood flow in the SMA gradually returned to a stable level，the wall pressure gradually decreased，and the WSS gradually increased to a stable state. Conclusion：Hemodynamic parameters of type Ⅰ and type Ⅱ SISMAD can gradually return to a stable state after conservative treatment，and therefore，conservative treatment，as the preferred strategy for type Ⅰ and type Ⅱ SISMAD，is safe and effective.