Flow patterns and classification within Spontaneous Isolated Superior Mesenteric Artery Dissection (SISMAD) are crucial for selecting subsequent treatment options. This study aims to propose a new classification of SISMAD and to propose two corresponding treatment plans based on this new classification. The 3D models of 70 patients with SISMAD were reconstructed and classified into Li types I-V based on morphology, followed by computational fluid dynamics analysis. The results show significant differences in blood flow patterns among patients with the same Li-type SISMAD, suggesting that the same treatment plan should not be applied universally. Based on the different blood flow conditions, a new classification of SISMAD is proposed (HX classification):​ Type I (dual-lumen flow type), subdivided into Ia and Ib;​ and Type II (single-lumen flow type). The simulation reveals that the rupture area of Type I SISMAD is related to the pressure difference between its true and false lumens, while the maximum-to-minimum diameter ratio of Type II SISMAD is associated with insufficient true lumen blood supply and lumen dilation. Furthermore, based on patient follow-up data and hemodynamic simulation results, corresponding treatment plans were proposed for the new classification:​ Type I was judged based on the ratio of rupture area to entrance area as a risk factor, and intervention treatment was recommended if the value was greater than 0.44;​ Type II can be judged as a risk factor based on the ratio of minimum diameter to maximum diameter, and if the value is less than 0.38, intervention treatment is recommended.