The global environment governance is an important agenda in today's international community. The subjects of governance are showing a diversified trend. New changes also emerge from the governance models, which develop from the centralized governance model to limited governance model and network governance model. Besides the national governments, the subjects of governance are divided into two categories:the Intergovernmental Organizations (IGO) and the International Non-governmental Organizations (INGO). This thesis analyzes the feasibility for Intergovernmental Organizations to replace the International Non-governmental Organizations in the global environmental governance. From the perspective of the requirement of the international community for the global environmental governance, Greenpeace International and United Nations Environment Programme (UNEP) are chosen as cases to conduct the comparative analysis and evaluation on the effectiveness.