Directed carotid cavernous fistula means high blood flow shunts between the internal carotid artery and the cavernous sinus. Obstructing the abnormal shunt between the internal carotid artery and the cavernous sinus while preserving the internal carotid artery is the key role in fistula treatment. Transarterial balloon embolization is currently the gold standard treatment for most of the carotid cavernous fistulas. But there are still some technical difficulties in the use of detachable balloon to treat carotid cavernous fistulas. Here, we describe undetachable balloon-assisted technique in the embolization of three patients who got complete immediate occlusion of the shunt and preserved the internal carotid artery at the same time.