Abstract: Objective To study the application of intraoperative color Doppler ultrasonography in intracranial giant aneurysm surgery. Methods Twenty-three patients with intracranial giant aneurysm were treated by clipping or by trapping the aneurysm in combination with bypass surgery. Color Doppler ultrasonography was conducted to examine the blood flow velocity in the aneurysml sac and its adjacent vessels before and after the aneurysm was clipped, or to examine the blood flow velocity and direction in the grafted vessels after trapping and bypass surgery. Results Four kinds of Doppler ultrasonography waves were observed in giant aneurysms. Of the 5 patients with their aneurysm directly clipped, 2 had stricture of tumor-carrying artery and its adjacent vessels. The grafted blood vessels were patent in all the 15 patients after bypass surgery. Conclusion Color Doppler ultrasonography is a feasible, safe, and reliable monitoring technique in giant aneurysm surgery.