Abstract: Kelasu tectonic belt is located in the northern Kuqa depression and the discovered subsalt large-deep gas field in the tectonic belt belongs to ultra-deep high-pressure gas fields with low-porosity high-yield fractured sandstones. Up to now 22 oil and gas reservoirs have been discovered in the gas field, which are the major production areas for natural gas in Tarim basin. There was no significant breakthrough after the discovery of Kela 2 gas field in 1998. Since 2006, the research of the deep zones in Kelasu tectonic belt has been strengthened, and in Aug., 2008 commercial gas flows were gained from the Cretaceous Bashijiqike formation in the Well Keshen-2 which is located in the Keshen-2 structure of Keshen area and the daily gas production was 40×104 m3, marking a great breakthrough has been gained. Then over 10 years of study, technological breakthroughs have been made on foreland basin exploration technology, petroleum geological theory and production practice, which provides guidance for the discovery of the Kelasu subsalt deep large gas field. The researches on trap identification in complex mountain areas, reservoir forming mechanism and hydrocarbon accumulation, speedy drilling and reservoir reformation effectively support the efficient exploration and development of the Kelasu subsalt deep large gas field