The magnetic characteristics and paleoclimatic implications of Late Pleistocene aeolian sediments in Central Asia have attracted wide attention. The loess on the north piedmont of the Tian Shan Mountain is one of the most important parts of aeolian deposits in Central Asian,and thus this region is an ideal place to study the aridification during the Late Cenozoic in the Asian interior. In this paper, we report the results of chronological, sedimentological, rock magnetic, geochemical and climatic studies of Late Pleistocene loess from the northern Chinese Tian Shan Mountain. The 173 loess samples were collected from the about 8.6m-thick Urumqi River section (URS: 43°30'02.77"N,87°19'26.53"E; elevation 1673m above sea level) with the vertical interval of 5cm in the southern Chaiwopu Basin of the northern Chinese Tian Shan foreland. Our results reveal: (1) Optically stimulated luminescence (OSL) dating constrains the time spans of URS loess sedimentation from ca.50ka to 14ka. (2) The investigation of grain size shows the URS loess grain size distribution is mainly dominated by the silt fraction (2 ~ 63 mum), while the contents of clay (< 2 mum) and sand (>63mum) are less. (3) The rock magnetic analysis indicates that medium-coercivity component of the URS loess contributes to the magnetic susceptibility, but the contribution of high-coercivity minerals to the magnetic properties is limited. The further analysis indicates that the pattern of rare earth elements (REEs) of URS is indicative of a possible stable source area of the URS loess deposits, thus change in source area cannot interpret the observed variations of rock magnetic parameters in the URS. Therefore, the sediment particle size composition plays a key role in the variations of magnetism of the URS loess sediments. This is confirmed by correlation analyses between the magnetic parameters (chi_(lf), chi_(ARM)/chi_(lf), and chi_(ARM)/SIRM) and the sediment grain size parameters (>63mum and median particle diameter) respectively, which indicates that the samples with higher chi_(lf) values contain coarser sediment grains as well as coarser magnetic grains. Finally, based on the result of grain size analysis of the URS, the paleoclimate history during Late Pleistocene in the Chaiwopu Basin was reconstructed as follows: although there were fluctuations,the general paleoclimate during Late Pleistocene in the Chaiwopu Basin of the northern Chinese Tian Shan foreland was characterized by aridity.