AIM: To investigate the ultrastructural pathogenesis of photodynamic therapy (PDT) for the experimental corneal neovascularization (CNV) by Hematoporphyrin Derivate (HPD) as photosensitizer and Argon laser as light source. METHODS: Experimental CNV models were induced in 7 white rabbits using alkali burn. Six weeks after models establishment, animals with CNV were injected with HPD intravenously, and 48 hours after the injection, 7 eyes were irradiated with argon laser (power 800mw, wavelength 514.5nm, spot diameter 200μm, exposure time 2ms). The irradiated CNV was observed by light microscopy and scanning electron microscopy. RESULTS: Histopathological study indicated that there was a striking decrease in the number of the CNV, vascular endothelium became degeneration and necrosis, some vessels were atrophy and attenuated, and vessels cavity were blocked by some thrombosis. No obvious abnormal histopathological findings were noted in surrounding tissues. CONCLUSION: The high precise action on CNV and minimal damage to surrounding tissues with PDT by HPD as photosensitizer suggested that PDT might be an effective and safe modality in the treatment of CNV.