【Objective】 To study the factors relative to the delayed diagnosis of spontaneous dual arteriovenous fistulas （DAVF）and its influence on the prognosis.【Methods】We included 102 continuous patients diagnosed DAVF in the First Affiliated Hospital of Sun Yat-sen University，and analyzed the correlative factors and impact on outcome of diagnostic delay. Outcome was whether symptoms were non-improvement，improvement or restoration at discharge.【Results】Median delay from onset to diagnosis was 3 months（interquartile range，1 to 6）. Compared with patients diagnosed earlier（diagnose time≤3 months），patients diag? nosed later（diagnose time＞3 months）had a lower frequency of headache（P = 0.012），ptosis（P = 0.035）and parenchymal lesions （P = 0.001），a higher frequency of conjunctival congestion（P = 0.004），tinnitus（P = 0.021），visual dysfunction（P＜0.001），iso? lated visual dysfunction（P = 0.007）and delayed imaging scan（P＜0.001），a higher frequency of endovascular treatment，and a lower frequency of improvement or restoration at discharge（P = 0.033），in which patients with visual dysfunction had a lower fre? quency of improvement or restoration than those without visual dysfunction（P = 0.023）. Compared to those with visual dysfunction and other symptoms，patients with isolated visual dysfunction had a higher frequency of onset with paroxysmal blurring or blinding （P＜0.001），two eyes involved（P＜0.001）and more severe visual loss（P = 0.057），a higher frequency of draining into transverse- sigmoid sinus（P＜0.001）instead of cavernous sinus（P＜0.001），and suffered intracranial hypertension all（median intracrani? al pressure，405 mmH 2 O；interquartile range，370 ~ 512 mmH 2 O）. However，no statistically significant differences were found in thefrequency of improvement or restoration at discharge between two groups（P = 0.739）.【Conclusion】Diagnostic delay was consider? able in this cohort and was associated with outcome，especially in patients with visual dysfunction.