Abstract: miRNAs regulated the transition from the vegetative to the reproductive growth in the flowering plants,whereas the evolution of this mechanism remained unknown.The fern was a key link in the evolution of land plants the miRNAs of the vegetative and the reproductive growths of Ceratopteris pteridoides were sequenced.42 conserved miRNA were identified,and seven miRNAs including miR397 were found firstly emerging in ferns.miR156 was downregulated in the reproductive phase in C.pteridoides,while its SPL target genes were simultaneously upregulated.miR172 contrastingly was upregulated in the reproductive phase,and at the same time AP2-like target genes were downregulated.The accumulation level of miR171 and miR159 also changed as expected,and thus the mechanism of miRNAs regulating the transition of growth phases might have been present in the primitive euphyllophyte.miR160/166/319/394 were related to the morphology of the downward incurvature of the fertile frond in C.pteridoides.tasi R-ARF production in C.pteridoides revealed the miR390-TAS3-ARF pathway firstly occurred in ferns.