Due to the important role of miRNA in regulation of plant gene expression, researchers have focused on the prediction, identification, functional and evolutionary analysis of miRNA. As genome sequencing has been completed in many species, the integration of genomic sequences with evolutionary data of miRNA provides more and more evidence and hypotheses for the origin and evolution of miRNA. However, the evolution of miRNA in plants has not been extensively reviewed. In this article, we reviewed several aspects of the evolution of miRNA in plants, including the origin hypothesis of miRNA, the birth and death of miRNA, and the functional evolution of miRNA, which provides a reference for future research.