The paired box gene 6(Pax6) is approximately 3 Mb long and located on mouse chromosome 2 and on human chromosome 11. In the both species, a CpG island is located near (and overlapped) the promoter of Pax6. Current researches suggest that PAX6 mutation is associated with cataract and it is a key gene involved in lens formation. To obtain insights into the aging cataract, we compared the expression level of Pax6 in different age groups lens of mouse. We also examined the DNA methylation status of the promoter regions of Pax6. Our data showed that Pax6 was highly expressed in youth, but rarely expressed in aging lens. Interestingly, the expression level of Pax6 in youth was almost twice that seen in the aging lens. The Pax6 promoter region was hyper-methylated in aging stage. Conversely, the promoter region of Pax6 was hypo-methylated in youth lens. These data support the DNA methylation status of the promoter regions of Pax6 is associated with Pax6 in mouse aging-lens process. Analysis of DNA methylation associated with gene expression in aging lens may help to explain the age related cataract occurring.