Mitogen-activated protein kinase (MAPK) signaling pathway plays important roles in the meiosis of oocytes. p90^rsk is the best known target of MAPK, which mediates multiple functions of MAPK during oocyte meiotic maturation, including the resumption of meiosis, the MⅠ/MⅡ transition and the sustain of MⅡ arrest. The phosphorylation of p90^rsk is the result of MAPK activation, and the dephosphorylation of p90^rsk is following the inactivation of MAPK at the end of meiosis. The progress of p90^rsk in oocytes is introduced.