Abstract:Abstract: In order to explore the application of the top air hydrocarbon technology in gas hydrates geochemical exploration in land permafrost region, the known natural gas hydrate mining area of Qilian Muli and the unknown Hala lake is chosen as the test area. The test indexes include soil top air、soil acid solution hydrocarbon、debris roof air logging and methane carbon isotope. The research shows that the methane as the main component of the top air hydrocarbon above the the known natural gas hydrate mining area of Qilian Muli is of high percentage, significantly higher than these conventional oil basins ,and 90.6 percent of C1 content is above 78%. In the plane, there is an obvious anomaly of soil top air methane above the mine, and on the section, there is “frontal halo”anomalous characteristics above the stable zone of the hydrate，the spatial distribution of which has close relation with Qilian mountain hydrate mineral spread distribution. The surface oil-gas geochemical anomaly is pyrolysis origin based on the judgment of methane carbon isotopes and hydrocarbons, the same origin as the gas hydrate of Qilian mountain permafrost region. There is no obvious characteristics of top air hydrocarbon anomaly in the Hala lake test area where natural gas hydrate is not discovered. The test result of geochemical exploration techniques of natural gas hydrates in the land area of permafrost region indicates that the technology can be used to determine the genetic type of hydrate, as well as can circle the range of hydrate deposits.