Abstract: Objective　To investigate the function of blood flow dynamic factors in nonarteritic anterior ischemic optic neuropathy(NAION).Methods　The brachial artery blood pressure, optic artery blood pressure and intraocular pressure (IOP) in 48 patients (50 eyes) with NAION and 50 patients (50 eyes) without NAION were comparatively studied.Results　Both the systolic and diastolic pressure of the brachial artery and optic artery in NAION group were significantly lower than those in non-NAION group (P<0.05), while the IOP in the NAION group was significantly higher than that in non-NAION group (P<0.05).Both the differences between the optic artery systolic pressure and IOP and bwteen the optic artery diastolic pressure and IOP in NAION group were significantly lower than those in non-NAION group (P<0.01).Conclusion　The relative hypotension and high IOP, and the imbalance between the optic artery blood pressure and IOP were the important causes in NAION.