AIM:To study the relation of oxygen therapy time and concentration and retinopathy of prematurity(ROP) stage.METHODS:The retina of premature infants with birth-weight ≤2500g and gestation-age ≤32 weeks are examined by indirect ophthalmoscope in 16 weeks.RESULTS:There are 43 cases(86 eyes) are diagnosed ROP.The pathological degree is more aggravated with the higher oxygen concentration and longer oxygen therapy time.When the oxygen concentration≥40%,retina pathological degree of 35.3% ROP infants are over III stage.When the time of oxygen therapy ≥7 days,retina pathological degree of 27.8% ROP infants are over III stage.CONCLUSION:The continuing low discharge oxygen therapy is criterion one.When the higher oxygen discharge is needed,the way to cut down oxygen discharge step by step can decrease the incidence of ROP.