Abstract: With the consumption and decreasing of the worldwide resources of petroleum and natural gas, the exports from various countries are working hard to find a new kind of substitute energy. Undoubtedly, a new hope in the future is probably attributed to the resource of gas hydrate following its discovery, exploration, development and utilization. For the significant strategies and economic benefits of gas hydrate, many developed countries and developing countries, such as United States, Japan, India, South Korea, Germany, Norway and China, have arranged it under the key national projects and invested enormous capital on the marine surveys and exploitation tests. In this review, the authors concisely describe the histories and current situations of gas hydrate in the main countries, with the emphasis placed on the national projects with the exploration extents, development situations, national investments and strategic deployments for gas hydrate. The authors also discuss the current progresses with which experts are most concerned. The authors divide those countries into 3 types:(1) United States. It has accumulated huge geological data and material supported by research institutions and ODP explorations in the early stage, but recently it somewhat reduces the investments on surveys and exploitation tests mainly because of the commercial success of shale gas revolution. In spite of such a situation, it still has great interest in theories and techniques of gas hydrate mainly focusing on the comprehensive subjects, and waits the opportunity to venture again once the market opportunity is ready. (2) China, Japan, India, South Korea. Due to the limits of domestic energy structures and preserve capacities, they hold an extremely active position on the development of gas hydrate with huge national investments on marine drilling expeditions. In particular, China and Japan have gained a great momentum in the marine exploitation tests, quite possibly being the first nations with full commercial operations. (3) Germany, Norway. As the traditional European industrial countries, they focus on improving gas hydrate exploitation techniques, for instance, the technology of CO₂-CH₄ replacement, paying much attention on environmental assessment supported by their solid industrial technical groundwork. They are the representatives of Greenpeace in the subject of gas hydrate and maybe provide a new opportunity in the later energy times for gas hydrate development.