Due to the facts that overseas workers will encounter many difficulties during their employment abroad,such as absence of social security,double payment of social security and payment barrier of social security payment etc.,western European countries began to explore the international cooperation of social security in the early twentieth century. The main way for them to do that is to sign international social security agreements among countries and reasonably undertake and share the responsibilities and benefits of the overseas workers’ social security. After the development for more than a century,the international cooperation of social security has entered a mature period from the exploration period,which not only has made great progress in the covering areas,benefiting people and the main content,but also has developed the cooperation from bilateral agreements to bilateral and multilateral agreements simultaneously,and it further has become an effective way to safeguard the rights and interests of overseas workers in the world.