Abstract: The decrease and control of space debris is of great importance for the flight safety of spacecraft and space activity of human. The Legal Mechanism of Space Debris Mitigation is the law and rule mode in order for the decrease of space debris generation and protection of spacecraft from space debris. The study of Legal Mechanism of Space Debris Mitigation includes five mechanisms of duty and right organizations, constraint and admission, pre-warning and protection, resource guarantee, and liability investigation. The interior lawmaking about the mitigation of space debris can mainly be divided into America mode and Russia mode. The America mode is characteristic of system of decentralization, and its legal norm contains different aspects of congress lawmaking, federal regulations and judicial precedent by excellent legislative technique, rich legal practice and high lawmaking quality. And Russia one is characteristic of system of centralization, with the emphasis on generality and guidance at law lay, and is restricted and regulated clearly and specially by technical standards.