Abstract: Objective: Comparative study the principles and applications of 320 Slice, 64 Slice CTA and rotation 3D DSA in diagnosis of intracranial aneurysms in order to choose the most appropriate inspection ways. Methods: The 86 patients who were highly suspected with intracranial aneurysms were examined by 320 slice CTA, 64 slice spiral CTA and had 3D DSA inspection at the same time. To conduct a comparative study of the characteristics of CTA and 3D DSA image. Results: 86 cases had been confirmed by operation and interventional procedures.92 cases were detected by 320 Slice CTA, 90 cases were detected by 64 slice CTA and 96 cases were detected by 3D DSA respectively, There was no significant difference between 320 slice, 64 slice CTA and 3D DSA(<i<P</i<<0.05). Conclusions: 320 Slice CTA, 64 Slice CTA and 3D DSA examination has their own advantage in the diagnosis of intracranial aneurysms. The 320 Slice CTA is a good method to diagnose aneurysms and is of the advantages including rapidness, noninvasive imaging and high accuracy. CTA are assistant tools for DSA in inspecting intracranial aneurysms. And the re-examination after the surgery still should be the first choice for screening in the patient with aneurysm. And 320 slice CTA is obviously superior to 64 slice CTA, 320-Slice CTA still cannot replace DSA and 3D RA because it may miss very small aneurysm.