Oocyte aging induces low pregnancy,increases abortion and causes more birth defects.In order to optimize the system for in vitro maturation and fertilization of oocytes,improve assisted reproductive technology(ART) and lower birth defects,it is theoretically and practically important to study the changes and mechanism of oocyte aging,and to explore the effective method for retarding this process.Thereby we make a brief review of the methods for oocyte aging studies,changes of spindle-associated proteins,mitochondria,ubiquitin,histone modification and DNA methylation modification during this process as well as its relations with cortical reaction,polyspermy and apoptosis.Factors affecting oocyte aging and molecular mechanisms of oocyte aging are also discussed.