The United Nations Convention Relating to the Statusof Refugees 1951 and its Protocol in 1967 set Four Essentials to limit the definition of "refugee". The concept of complementary protec-tion emerged in academia and practice for those who, though they do not have the essentials, are in need of protection. Complementary protection is considered not only a moral obligation, but also a le-gal obligation. Although as the result of developing the principle of"non-refoulement" in inteational law, "complementary protection"should be limited when economic and social rights are conceed. The development of the non-refoulement principle and the emergence of"complementary protection" are based on the Erga Omnes of human rights. The Inteational Court of Justice has restricted the emergence and evolvement of obligations Erga Omnes within the scope of obliga-tions conceing fundamental and non-derogable human rights, and therefore, the application of "complementary protection" in protecting economic and social rights has been limited. Only when the unbalance of economic and social rights has been serious enough to impact other fundamental human rights will the obligation of "complementary pro-tection" ensue.