Objective: To investigate the relationship between low ocular perfusion pressure (OPP) with acute non-arterial anterior ischemic optic neuropathy (ANAION).Methods: Forty- six patients (46 eyes) with ANAION from July 2010 to December 2016 were retrospectively analyzed. The 24-h intraocualr pressure (IOP) in sitting position was measured by non-contact tonometer. The brachial artery systolic blood pressure (SBP) and diastolic blood pressure (DBP) were simultaneously measured by electrocardiogram monitor. The 24-h OPP was calculated according to the measured blood pressure and intraocular pressure: OPP= 45% DBP-IOP. OPP< 10mmHg was defined as low OPP. Sudden visual acuity declining or visual field defect was recorded as the attack of ANAION. 24h was divided into four periods: period A (1-6 A.M), period B (6-12 A.M), period C (12-18 P.M) and period D (18-24 P.M). The correlation between low OPP and ANAION was analyzed. Statistical method was used by Person correlation analysis.Results: There was a statistical difference in the low OPP in the four periods (P< 0.05). The most common period of low OPP was period A (1-6 A.M), with the incidence of low OPP as high as 58.3%. There was a statistical difference in the incidence of ANAION in the four periods (P< 0.05). Most common time period of ANAION was also period A (1-6 A.M), with the incidence rate as high as 46.3%. Person correlation analysis showed that the period of low OPP was associated with the period of ANAION onset (r=0.934, P < 0.05).Conclusion: There was a significant clinical correlation between low OPP and ANAION. Period A (1-6 A.M) was the high-risk period for low OPP and ANAION. The occurrence of ANAION can be reduced by elevating the OPP to improve the blood perfusion of the anterior optic nerve.