Abstract: Objective To evaluate the regional anatomy between the abdominal autonomic nerves including the abdominal aortic plexus (AAP) and the inferior mesenteric artery (IMA), and explore the safe ligation point on the IMA and the optimal dissection method to avoid autonomic nerve injuries. Methods and Results Dissections and observation were carried out on 16 fixed male cadavers. The AAP located in the thin fascia layer covering the surface of the aorta and its branches. No autonomic nerves were found in the area around the root of the IMA, and the point where the IMA and the left trunk of the AAP intersected was highly variable. The left trunk of the AAP adhered more closely to the IMA than to the aorta. Conclusions In view of autonomic nerve preservation, the only safe site for ligation of the IMA is at its origin, and no other such sites are available a-long the IMA trunk and its branches. The IMA and the posterior fascia layer containing the autonomic nerves constitute the optimal surgical plane for IMA ligation, which should be performed following skeletonization of the IMA with careful preservation of the integrity of the posterior fascia layer.