MicroRNAs (miRNAs) are a class of ～22 nt noncoding regulatory RNAs which are universal in eukaryotes. They act as negative regulator of gene expression by targeting mRNAs for cleavage or translational repression. miRNAs widely participate in regulation of gene expression associated with plant developmental processes, such as organs morphogenesis and signal transduction pathway in plants. Similar to antiviral RNA silencing in plants, miRNA pathway is also interfered by silencing suppressors encoded by viruses. In this review we give a brief summary of the differences between miRNA-mediated regulatory pathway and siRNA-mediated RNA silencing. In particular, we review the recent studies on miRNA regulatory roles in plant developmental processes, as well as the interference of viral suppressors in miRNA pathway, aiming to get an insight into the complexity of gene expression regulation in eukaryotic organisms.