To understand the radial growth of Mongolian pine (Pinus sylvestris var.mongolica) and its response to climate at different competition intensities,the tree-ring width chronology and its competition of Mongolian pine in Hulunbuir Sandy Land was analyzed using tree chronology analysis and competitive index.Results showed that competition significantly affected the radial growth of Mongolian pine.For the radial growth,large trees with low competition were more sensitive to the monthly average maximum temperature,precipitation,and relative humidity of the growing season,while small trees with low competition index were more sensitive to the lowest monthly temperature,precipitation and relative humidity in the previous years growing season.Drought had greater impact on large trees and small trees than on medium-sized trees,especially on large trees with strong competitiveness.In general,the radial growth and climate response of Mongolian pine in Hulunbeier Sandy Land were significantly affected by the competition.Our results provide scientific basis for the management of natural Mongolian pine forests under the background of climate change.