Natural gas hydrate is a possible clean and sustainable energy source because of its high energy density, wide distribution and enormous reserves. Many countries have included the exploitation of gas hydrate in their national development plan and have carried out studies of basic properties of natural gas hydrate and field tests in permafrost and on the seafloor. However, the present theories and technologies are not enough to overcome the challenges for commercial production. These are: 1) Environmental and geological risks and low gas production efficiency. 2) Lack of drilling and completion technologies for natural gas hydrate. 3) Difficulty in separation of gas and water for mass water yield during production of gas hydrate. 4) No solutions for economic production of gas hydrate with high energy efficiency. To realize the safe and efficient production of gas hydrate, the following four key technologies need to be investigated: Reconstruction and protection of gas hydrate reservoirs; Specialized drilling and completion technologies; Technologies for rapid efficient downhole separation of gas and water; Enhancement of energy efficiency.