In the world society，international nongovernmental organizations（INGOs）act as the main body of the global third sector，which carries on activities outside the business and political realms. Despite the recent upsurge of attention to the INGOs，little is known about the global third sector. Since 1850，INGOs has experienced several important periods，the formative period—late 19th century，during which the founded INGOs had the ideology of one world；the interwar period—a wave of disrupted transnationalization；the postwar period—INGOs expand rapidly. After the World War II，many types of regional INGOs emerged. By the beginning of the 21st century，INGOs cover almost every type of human activities. INGOs carry out three principal types of activities：they gather，produce，and disseminate mountains of information；they sponsor kinds of meetings；they attempt to influence other actors in the world society. Most well-known INGOs focus on the environment，human rights，development issues，etc.，but these sectors constitute only a small portion of the INGO population. With the increased attention to civil society，INGOs as the spokespersons play an important role in global governance，even a dominant role in many social issues. In the global governance processes，INGO relationships with states，IGOs and transnational corporations have become dense and complex.