The clastic rocks in sedimentary basins recorded the information of its adjacent mountain uplifting and tectonic evolution. In this paper the detrital Muscovites from Cretaceous sandstone in the Kuqa basin were analysed by electron microprobe and 40Ar/39Ar dating. A systematic comparison of the geochemical compositions and 40Ar/39Ar ages of Muscovite between Cretaceous sandstone in the Kuqa basin and metamorphic rocks in Tianshan orogen, indicated that Muscovites from Cretaceous sandstone are phengites. The phengites from Cretaceous sandstone has less Si content than them from blueschist and eclogite in southwestern Tianshan, which suggested the pressures in detrital phengites were lower than those preserved in blueschist and eclogite of the present Tianshan. The 40Ar/39Ar phengite age of 396.6 Ma from Cretaceous sandstone is consistent with the ages of 419-310 Ma from the high pressure-low temperature rocks in southwestern Tianshan, which indicated during Cretaceous the high pressure-low temperature rocks had been exhumed at surface and served as the provenance for Kuqa basin. It has been concluded that during Cretaceous the high pressure-low temperature rocks were higher in elevation than the Haerke Mountain which located between the Kuqa basin and the high pressure-low temperature rocks, however, the present geomorphology of the Tianshan indicated that the high pressure-low temperature rocks had lower elevation compared with the Haerke Mountain, which was more likely caused by differential uplift and exhumation of Tianshan in Cenozoic.