RNA silencing is a supervising mechanism in eukaryote which can prevent virus duplication, repress transposition of transposon and regulate gene expression. Compared with that in animals, RNA silencing in plants shows some differences in the function of RdRP, in bi-directional transitive RNAi, and in systemic propagation, etc. Meanwhile,the endogenous small RNAs in plants are more diverse than those in animals. In this paper, it is reviewed of the mechanism of RNA silencing in plants and the possibility of its use in plant functional Genomics.