There remained concerns about the sustainability of social security system in advanced economies.The sustainability of social security system corresponds to a state which can be maintained to provide adequate social protection for people over the foreseeable decades.In addressing major challengers，EU clearly seeks to strike a balance between maintaining fiscal sustainability and maintaining social adequacy.After social security system has been put on a more sustainable development track，the social security policy have to focus more on social sustainability.Finally，some reflections can be given.