The gas hydrate is considered a clean optional energy for "fossil fuels" in the 21 Century, which is of great importance for humans on the Earth. The South China Sea is the potential area for the occurrence of gas hy-drates. This study applies satellite-based thermal infrared remote sensing (STIRS) to prospecting for gas hy-drates in the South China Sea for the first time, which proves to be effective.This paper analyses the mechanism of high temperature shown in STIRS images. The relationship between the high temperature and the occurrence of conventional oil (gas) reserves and gas hydrates is also discussed. It is pointed out that the high temperature is caused by the seepage of gases such as CH4 and CO2 from convention-al oil gas fields in shallow water and by that from marine gas hydrates in deep water, but is almost not related to gases from the deep crust. The areas of high temperature shown in the STIRS images are mainly distributed in the Xisha trough, Dongsha Island slopes, Bijianan basin and Nanaha trough of the South China Sea, show-ing potentials for gas hydrates to grow. In these areas, there exist some other known indicators, such as BSR and geochemical and radioactive anomalies, for gas hydrates to occur. Therefore, in the South China Sea, the high temperature shown in the STIRS images before earthquakes can give an indirect evidence for the existence of marine gas hydrates in deep water.