The associated weed population is a common phenomenon in agricultural production during the growth of crops,and the remains of weeds are often found apart from the crops in ancient remains. Many scholars try to establish the proportional relationship model between weed and crop quantity to reconstruct the planting and processing process of ancient crops. A large number of settlement sites dating from 1000 BC are distributed in Barkol Grassland of Xinjiang. Northwest University,in cooperation with Xinjiang Institute of Cultural Relics and Archaeology,Hami Bureau of Cultural Heritage and Barkol County Bureau of Cultural Heritage,has carried out archaeological investigations,excavations and research on these sites for more than a decade. This study analyzes the ratio and change of the number of crops,large weeds and small weeds by systematically flotation,observation and classification of the archaeobotanical samples collected from settlement structures,and then discusses the possible relationship between the changes of crop planting and treatment,the evolution of living mode of ancient residents of Barkol grassland and environmental changes in the millennium BC.