Partitioning of subpopulations in bulk grain-size distribution and identification of their sedimentary implications has become a fundamental task for further studies on quantitative reconstruction of the sedimentary environment. The subpopulations were identified through calculating standard deviation of each grain-size class of the six profiles of the loess-paleosal formed during the last interglacial-glacial cycle in the west of the Loess Plateau, Hexi Corridor and the west of Henan Province, China. The peak values of standard deviation corresponded to the modal grain-sizes of each environmentally sensitive grain-size population. Findings of the study indicate that the two major grain-size populations (coarse and fine) varied from profile to profile, suggesting different sedimental implications. Distance of material resources and post-sedimental pedogenesis are the two major affecting factors on environmentally sensitive grain-size populations. The sensitive grain-size populations of Binggou and Luojiawan profiles were coarser because they were more influenced by the distance of material resources; whereas the sensitive grain-size populations of Nuanhuowan and Kouma profile were finer as they were more influenced by the pedogenesis. The results showed similar populations and subpopulations. The analysis of the standard deviation of each grain-size class of Koma profile demonstrated comparability between the population and L₁, which deposited during the last glacial period, and that big difference between the population and S₁, which deposited during the last interglacial period, suggesting close relationship with pedogenesis.