As one of the most important parts of the natural gas hydrate system,the study of environmental effect is critical to safe exploration and development of gas hydrate.The unique seafloor ecosystems supported by gas hydrate,the important geological and environmental issues involved and the geat potential as a new energy reserve are all attractive and challenging new fields of science for the human society.In this review,we inspected the most current survey and research work in this field world widely,and explicitly put forward the three kinds of environmental effects,i.e.the biological effect,chemical effect and physical effect,and especially highlighted the fundamental questions and key issues in this field.Our ultimate goal is to prospect the trend and needs of environmental effect in the future development of natural gas hydrate,provide some necessary references for the survey and assessment of gas hydrate,so as to attract comprehensive interests in the questions from the society.