Purpose: We evaluated the effect of heated and humidified high flow nasal cannula (HFNC) oxygen supplementation to promote regression of high-risk prethreshold retinopathy of prematurity (Hrp-ROP) in premature infants. Methods: A prospective study was designed for Hrp-ROP premature infants undergoing HFNC oxygen supplementation to evaluate its capacity for promoting ROP regression. Statistical analysis with independent samples t-tests and Fisher's exact tests was performed, and forest plots were created to illuminate the odds ratio of factors associated with ROP regression as well as HFNC complication. Results: With HFNC, 16 of 20 infants with Hrp-ROP experienced regression, which is higher than the natural regression rate, comparing to the data in other clinical trials (52% in the STOP-ROP study). Among four progressed ROP infants, three were treated with laser photocoagulation and one received anti-vascular endothelial growth factor (VEGF) therapy. The anti-VEGF treated patient encountered ROP recurrence one month after injection and was treated successfully by additional HFNC. No significant differences between regression and progression cases were found for gestational age, birth weight, plus disease, age for HFNC, and SO2 level. The blood saturation of oxygen was significantly increased after HFNC (92 6 1.3% vs. 96.6 +/- 6 0.8%, P < 0.001), while the heartbeat rate (HR) and respiratory rate (RR) had no significant differences (139.4 +/- 6 5.4 vs. 140.6 +/- 6 4.5, P = -0.409; 37.7 +/- 6 2.3 vs. 37 6 +/- 1.9, P = 0.330, respectively). The main complication of HNFC was nasal erosion associated with airflow and HFNC duration (RR = 1.8, P = 0.026; RR = 1.8, P = 0.026, respectively). Conclusions: The progression of Hrp-ROP was significantly decreased after HFNC oxygen supplementation with slightly tolerable complication. Translational Relevance: Our study suggests that HNFC can be an alternative treatment for Hrp-ROP, potentially avoiding the problems caused by other invasive treatment.