AIM: To observe the neovascularization process with no intervention in rat allogenic penetrating keratoplasty. METHODS: Allogenic penetrating keratoplasties were successfully performed in 34 female SPF SD rats with no intervention after operations. Corneal neovascularization (CNV) process was noted on day 4, 7, 15 and 30 with operating microscope. The vascular area surface was calculated using the formula C /12×3.14×[r ²-(r -I )²]. RESULTS: CNV was noted in 29 out of 34 rats (85%). Firstly, the new vessels distributed around the cornea like a brush then gradually extended towards the center. The vessels were distorted and massive with branched tails, they continued growing to reticulated veins in peak time then gradually atrophied. The average neovascularization area (SE) on day 4, 7, 15 and 30 was 11.8±3.5mm², 18.5±4.0mm²,14.4±4.3mm² and 6.0±1.8mm², respectively and 12.7±1.9mm² in total. The average percentage that new vessels accounting the whole cornea area (SE) was 30.8%±8.7%, 65.3%±12.8%, 59.4%±14.5%,36.2%±10.9% and 48.7%±6.4% in total. CONCLUSION: In rat allogenic penetrating keratoplasties without intervention, CNV presents on day 4 and reaches the maximum area on day 7. Then the vessels gradually atrophies, about 50% of the maximum area still remains on day 30.