Abstract The flysch of Maerzheng Formation in the Buqingshan Area is located in the Southern margin of the East Kunlun region,and it’s main body is a set of turbidite of deposition in the bathyal—abyssal environment.This paper studied the characteristics of sandstone of the flysch formation.The framework component of the Maerzheng Formation sandstones statistical results show that it’s mainly feldspathic litharenite,it’s quartz, feldspar，lithic respectively is 42%,37%，21%,the provenance is mainly divided recycled island arc and orogenic belt in category.The sandstones of Maerzheng Formation show that w（SiO2） values of 50.18%～74.05%,average value of 66.69%,CIA=43～69,∑REE values of 59.99×10-6～171.07×10-6,∑LREE/∑HREE=6.6～8.8;LaN/YbN=6.6～10.7,LaN/SmN=3.2～4.6,δEu=0.59～1.04.The sandstone’s geochemical characteristic indicate that the flysch was formed in the tectonic setting of the active continental margin;the sandstone belong to continental island arc type ;the provenance is the volcanic～plutonic magmatic island arc orogene and metamorphic basement of northern East Kunlun block;the protolith of sandstone dominantly derived from felsic volcanic rocks,cogenetic plutonic and metamorphic rock of basement;the sedimentary basin is the ancient trench or fore～arc setting in the outside subduction complex.Consequently,it indirectly record that the process of Buqingshan—A’nyemaqen Ocean continued expand—subduction for Northward—finally close.