Objectives To observe the characteristics of occurrence a nd progres s of retinopathy of prematurity (ROP) in premature infants and search the reason able ROP screening time and therapeutic methods.〓〖WTHZ〗Methods〓〖WTBZ〗ROP s creening was perf ormed on 829 infants, with the gestational agele;35 weeks and the birth weightle; 2000 g, by indirect ophthalmoscopy combined with scleral pressurizing implement. Thirtytwo infants with prethreshold type I and threshold ROP underwent cryot he rapy. The followup duration after the operation was 316 months, and the crit er ia of the control of the diseases included: alleviation of the plus disease, all eviation of the vascular ridge, formation of the cryospots, absorption of vitr e oretinal hemorrhage, and non bad retinal structure. If the disease was not contr olled, recryotherapy or vitrectomy would be carried out.〓〖WTHZ〗Results〓〖W TBZ〗ROP was fou nd in 86 infants (172 eyes). The difference of oxygen duration time among ROP g roups and nonROP group was significant; the occurrence rate of ROP in the infa n ts with the birth weightle;1000 g, 10011500 g and 15012000 g was 6956%, 16 38% , and 414%, respectively; the occurrence rate of ROP in the infants with the g estat ional agele;30 weeks, 3132 weeks, and 3335 weeks was 37.14%, 10.43%, and 2.91 %, respectively; the occurrence rate of ROP in singleembryo infants group and mul t iple embryo infants group was 7.52% and 20.22%, respectively. Favorable outcom e was observed in 30 out of 32 infants who had undergone cryotherapy; 2 infants d eveloped retinal detachment with plus disease and peripheral retinal hemorrhage. The sccess rate of cryotherapy is high in the infants with the gestational age lt;32 weeks.〓〖WTHZ〗Conclusions〓〖WTBZ〗The ROP incidence rate is higher in the infants with lo ng oxygenbreathing duration, birth weighle;1000 g, and gestational age le; 32 we ek infants, which should be screened carefully. The infants having ROP onset within 32 weeks, with plus disease, and peripheral retinal hemorrhage should be follow ed up closely. The prognosis of cryotherapy for type I prethreshold and thresh old ROP is good and the operation is safe.