Leber's hereditary optic neuropathy(LHON)is a maternally inherited blinding disease. The clinical phenotype of LHON is the degeneration of retinal ganglion cells(RGCs)and a progressive degeneration of the optic nerve. Three common mutations, G11778A, T14484C and G3460A are responsible for over 90% of cases. Differences in penetrance indicate the additional modifier genes influencing penetrance of the mitochondrial DNA mutation for LHON patients. Different types of mitochondrial haplogroups, environmental factors also have different effects on the penetrance of the mitochondrial DNA mutations. In the present paper, here the progress of the factors influencing the penetrance of Leber's hereditary optic neuropathy will be summarized.