DNA methylation is an important epigenetic modification and multiple factors interact to regulate the establishment and maintenance of DNA methylation in plant genome. Different methylation sites require different cytosine methyltransferases, which contribute to the modification of chromatin structure and mediate epigenetics with chromatin remodeling enzymes and histone modifying factors. DNA glycosylases can remove DNA methylation and alleviate silencing. The functions and interactions of DNA methylation regulating factors, the establishment, maintenance and removement mechanisms of DNA methylations are reviewed in this paper.