Abstract: As an important system of environmental management, since its promulgation in 1969, environmental impact assessment (EIA) has undergone continuous revision and improvement globally. Especially in the past ten years, under different political and economic backgrounds, the development of EIA reforms in the three largest economies, the United States, China and the European Union, have all shown common trends of simplifying the administrative procedures and improving the quality of the EIA procedure and reports. The Multiple Stream Framework (MSF) was adopted to conduct a comparative study on the causes, dynamics and trends of EIA system reform in the selected countries/regions. The research showed that the main reason for the EIA reform lied in the practical feedback of policies under different national conditions, the awakening of public awareness of environmental protection as well as market pressure.