Abstract: Significant progresses have been made so far for understanding of the occurrence, distribution and characteristics of natural gas hydrate, and a series of gas production tests from the permafrost and marine hydrate deposits have been carried out all over the world. However, the gas hydrate exploitation is still facing severe scientific challenges. Based on a general review of the global gas hydrate exploration and exploitation, this paper expounded the gas hydrate reservoir classification and geological controlling factors, and put forward four aspects of scientific challenges for the effective economic exploitation, including the resource evaluation, exploitation method and technology, reservoir geological parameters and engineering geological risks. In order to realize the effective economic exploitation of gas hydrate, the resource evaluation is the foundation, and the exploitation method and technology is the key. To determine whether the gas hydrate reservoir can be exploited requires the accurate reservoir geological parameters, and whether the effective exploitation can be realized depends on the control of engineering geological risks.