Abstract: The Cretaceous reservoir in Kuqa depression of Tarim basin is a set of ultra?deep, ultra?high pressure, high temperature and lowporosity fractured sandstones. To identify characteristics, genesis and exploration potential of the reservoir, an integrated research is performed using structural evolution reconstruction and systematical characterization and based on the data of confocal laser scanning, industrial CT, high?pressure mercury injection, SEM, carbon and oxygen isotopes analysis, physical properties of full?diameter cores, electron microprobe spectroscopy and so on. The study shows that the braided delta?front sand bodies are superimposed and distributed continuously in Cretaceous Bashijiqike formation of Crassus deep zones with the thickness of 150~250 m; in ultra?deep layers, residual primary porosity and dissolved pores are relatively developed, netlike, high?angle, filled to semi?filled fractures are developed, too. The reservoir generally belongs to low?porosity, medium?low permeability in nature; the genesis mechanism is dominated by 3 mechanisms such as shallow burial during the early and middle stages, celling structure of nappe?type, gypsum?salt rocks during the late stage and intercoupling and superimposition between dissolution during epidiagenetic stage to early diagenesis stage and tectonic compression at the late stage; the effective reservoir thickness ranges from 80 m to 200 m and the relatively high quality reservoir thickness reaches to 30~90 m, which are mainly continuously distributed in the areas superimposed by underwater distributary channel, E?W axis of structural anticline and zone within 220 m to unconformity surface. The effective reservoirs could still exist in the burial depth of 8 000 m. All the areas may have natural gas reserves potentials of trillions of cubic meters by estimation