DNA Methylation，most occurs in CpG dinucleotides， is a kind of epigenetic modification,most occurs in CpG dinucleotides。 The most striking feature of DNA methylation patterns is that the addition of a methyl group at the 5-position of cytosine in CpG dinucleotides by DNA methytransferase. It take for S-adenosylmethionine as methyl donor. DNA methylation has essential roles in many plant life processes. The characteristics of plant methylation，its regulating mechanisms, the effects on plants and the application of DNA methylation will be reviewed in this paper, providing a theoretical references to DNA methylation research on plant genetics.