Investigation of Chinchilla rabbits' corneal losions induced by 308 nm excimer laser was presented. The damage mechanism was the same as photo-chemical and there were two phases of reaction of immediate damage and delayed ones. By statistical analysis, the immediately corneal injury threshold (ED50) of 0.485 J/cm2 was obtained and its 90% confidence limit was 0.349～0.608 J/cm2. The delayed reaction appeared 6～18 hours after the irradiation.